Apparatus and associated methodology of imparting content protection to optically recorded data for secure reproduction

ABSTRACT

Described herewith is an optical disk manufacturing apparatus for reading recorded digital data from an optical disk, comprising an encryption unit ( 22, 23 ) for encrypting entered digital data according to a plurality of key information; an optical disk substrate manufacturing unit  2  for manufacturing an optical disk substrate  4  on which the encrypted digital data and key information are recorded in the form of physical form changes; a reflection film forming unit  41  for forming a reflection film on the optical disk substrate  4;  and a key information recording unit  7  for recording key information on the optical disk substrate on which the reflection film is formed. The reflection factor of the optical disk is changed locally, thereby giving a jitter to the position information of each pit edge, and desired data is recorded additionally according to this jitter. Pits, etc. are disposed so as to be deviated from the track center towards the inner/outer region of the optical disk  2,  thereby recording such subdata as key information KY, etc.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/412,864, filed on Oct. 5, 1999 now U.S. Pat. No. 6,665,240, and theparent claims priority under 35 USC 1.119 of Japanese Patent Nos.10-285516, of Oct. 7, 1998, 10-332222, of Nov. 24, 1998, and 10-371795,of Dec. 28, 1998, the entire contents of the parent application and theJapanese application are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and a method formanufacturing an optical disk, an apparatus and a method for recordingdata on the optical disk, and an apparatus and a method for reproducingdata from the optical disk, as well as the optical disk. For example,the present invention can apply to a compact disk, a compact diskplayer, an optical disk for recording audio data, and a recordingapparatus and a reproducing apparatus usable for the optical disk.

The present invention changes the reflectance of the optical disklocally, thereby giving a jitter to the positional information of eachpit edge, so that desired data is recorded on the optical diskadditionally. Consequently, various data can be recorded on the opticaldisk so as to be reproduced by an optical pickup for reproducing datastrings and not to be copied illegally without any adverse effect on thereproduction of the data strings recorded in the from of pit strings.

In addition, the present invention deviates bits, etc. towards theinner/outer region of the optical disk, thereby recording such subdataas key information, etc., so that various data can be recorded on theoptical disk so as to be reproduced by an optical pickup for reproducingthe data strings and not to be copied illegally without any adverseeffect on the reproduction of the data strings recorded in the form ofpit strings.

2. Description of the Related Art

In the case of conventional compact disks (CD), data strings to berecorded have been processed, then subjected to EFM modulation (Eight toFourteen Modulation), thereby such data as audio data is recorded.

On the other hand, a management data recording area is formed in thelead-in area provided in the inner region of the optical disk and theTOC (Table Of Contents) recorded in this recording area is used toselectively reproduce desired musical performance data, etc.

A compact disk having various recorded data as described above isprovided with a recording area for the IFPI (International Federation ofthe Photographic Industry) code in an inner area of the lead-in area,where such signals as audio signals and the TOC (Table Of Contents) usedby the object user are recorded. This area also has such inscriptioncodes as factory name, the disk number, etc., with which the history ofthe compact disk can be checked visually.

By the way, such the inscription data as a maker name, a factory name, adisk number, etc. are enscrolled on each compact disk so that thehistory of the compact disk is checked visually and such the inscriptiondata is used for discriminating illegally copied disks manufactured froman original disk. However, because such the inscription data is recordedso as to be checked visually, the inscription data arises a problem thatthe data cannot be reproduced easily by an optical pickup of the compactdisk player. In order to solve this problem, therefore, a reproducingmechanism is required dedicatedly for reproducing the inscription datawhile it is enabled to discriminate this inscription data from illegallycopied disks.

The inscription data to be recorded with those methods is recorded inthe form of pits ordinarily and checked visually, if it can beduplicated by, for example, creating a stamper by peeling bothprotection film and aluminum reflection film from the object compactdisk. And, this is why the compact disk cannot be protected from illegalcopying.

To solve the above-mentioned problems, for example, Japanese PatentLaid-Open No. 9-67843 discloses a method in which the output of arecording laser is varied to change the pit width recorded on the disk,thereby recording the inherent code on the disk.

For example, as the first example, there is a well-known method in whicha recording signal on a disk is encrypted and key information fordecryption is recorded as a variation of the pit width according to themethod described in the above-mentioned patent application. Areproducing apparatus is composed so that the key information recordedas described above is detected and the cryptogram is decrypted accordingto the detected key information. Because the key information is notrecorded on the pirated disk, the cryptogram is therefore not decryptedand the content of the disk is not reproduced normally. Therefore, if areproducing apparatus is composed as described above, then the pirateddisk becomes useless, thereby the pirated copy is substantiallyprevented.

Now, there are two well-known methods for making a pirated disk; amethod in which reproduced signal from a disk is supplied to a recordingunit as is and the other method in which the physical configuration of adisk is transferred as is. If a disk which is manufactured according tothe above-mentioned first example is used for making a pirated diskaccording to the method in which the reproduced signal is supplied to arecording unit as is, then the key information recorded in the form ofpit width change is not recorded on the pirated disk though theinformation recorded in the form of “pit/no pit” change is recorded inthe pirated disk. Therefore it is possible to prevent making of apirated disk according to the method in which the reproduced signal issupplied to a recording unit as is by employing the method described inthe first example. However, if a disk which is manufactured accordingthe above-mentioned first example is used for making a pirated diskaccording to the method in which the physical configuration of a disk istransferred, then the key information recorded in the form of pit widthchange is also copied to a pirated disk. Therefore, the first examplemethod is disadvantageous in that making of a pirated disk according tophysical transfer can not be prevented.

Now, the second example is known as a method for solving such a problem.In the second example, the key information is recorded not in the formof physical configuration but in the form of reflectance change. Indetail, a groove is formed on an area such as the lead-out area of anoptical disk, an intensive laser beam is irradiated onto the reflectionfilm of this area, thereby changing the reflection characteristic, andthe same information as that of a bit string is recorded.

If the key information is recorded in the form of reflectance change,the key information is recorded in the form of reflection characteristicchange of a reflection film. Because the key information is not recordedin the form of physical configuration (pit), the key information willnot be copied on the pirated disk which is made according to physicaltransfer. Therefore, this method complements the disadvantage of thefirst example, and it is possible to prevent the making of the pirateddisk by the use of the method according to physical transfer.

However, the second example is also disadvantageous in that if a pirateddisk is made according to the method in which the reproduced signal issupplied to a recording unit as is, the key information recorded on thelead-out area is copied as is.

As described above, the respective methods for preventing the pirateddisk which is proposed are effective only on either of the two methodsfor making a pirated disk herein addressed. Furthermore, if a piratedoptical disk is made according to a method not described above, thesemethods are entirely not effective.

Under such the circumstances, it is an object of the present inventionto provide an apparatus and a method for manufacturing an optical diskfrom which no pirated optical disk can be produced by any of a method inwhich the reproduced signal is supplied directly to a recording unit anda method in which the configuration of the optical disk is transferredphysically, thereby eliminating the disadvantage of the conventionalpirated copying method, and an optical disk to which such pirated copyprevention is applied and a method for reproducing an optical disk towhich such pirated copy prevention is applied.

Besides that, it will also be possible to reject an illegal copy withthe use of this data if various data can be recorded so as to bereproduced with an optical pickup for reproducing audio data and to bedifficult to copy illegally without any adverse effect on thereproduction of audio data as pit strings.

SUMMARY OF THE INVENTION

It is therefore another object of the present invention to provide anoptical disk, an optical disk recording unit, an optical disk recordingmethod, an optical disk reproducing apparatus, and an optical diskreproducing method which can record various data for inhibiting illegalcopying so as to be reproduced with an optical pickup for reproducingdata recorded in the form of a pit string, etc. and to be difficult tocopy illegally without any adverse effect on the reproduction of datarecorded in the format of a pit string, etc.

In order to solve the above conventional problems, an optical diskmanufacturing apparatus in accordance with the first present inventionfor manufacturing an optical disk having recorded digital data to beread out by irradiation of a laser beam comprises an encryption unit forencrypting input digital data according to a plurality of keyinformation, an optical disk substrate manufacturing machine formanufacturing an optical disk substrate on which the encrypted digitaldata and the key information are recorded in the form of physicalconfigurational change, a reflection film forming unit for forming areflection film on the optical disk substrate, and a key informationrecording unit for recording the key information on the optical disksubstrate having the reflection film thereon.

According to such the first present invention, the encryption unitencrypts input digital data according to a plurality of key information,the optical disk substrate manufacturing unit manufactures an opticaldisk substrate on which the encrypted digital data and key informationare recorded in the form of physical configurational change, thereflection film forming unit forms a reflection film on the optical disksubstrate, and the key information recording unit records the keyinformation on the optical disk substrate on which the reflection filmis formed.

The first present invention provides an optical disk manufacturingapparatus for manufacturing an optical disk having recorded digital datato be read out by irradiation of a laser beam comprising an encryptionunit for encrypting input digital data according to a plurality of keyinformation, an optical disk substrate manufacturing machine formanufacturing an optical disk substrate on which the encrypted digitaldata and the key information are recorded in the form of physicalconfigurational change, a reflection film forming unit for forming areflection film on the optical disk substrate, and a key informationrecording unit for recording the key information on the optical disksubstrate having the reflection film thereon.

The second present invention provides an optical disk manufacturingapparatus, wherein the optical disk substrate manufacturing unitcomprises an exposing unit for converging a laser beam on an opticaldisk according to the encrypted digital data and the key information toexpose the optical master disk, a stamper forming unit for forming astamper by applying a chemical treatment on the exposed optical masterdisk, thereby changing the physical configuration thereof, and aduplication unit for transferring the physical configurational change onthe stamper, thereby generating a plurality of optical disk substrates.

The third present invention provides an optical disk manufacturingapparatus, wherein the exposing unit comprises a laser beam intensitymodulation unit for modulating the intensity of the laser beam accordingto the encrypted digital data, and a laser beam convergent positionchanging unit for changing the convergent position of the laser beamaccording to the key information.

The fourth present invention provides an optical disk manufacturingapparatus, wherein the laser beam intensity changing unit comprises amodulation unit for generating a modulated signal according to theencrypted digital data, and an optical modulation unit for controllingthe on/off of the laser beam according to the modulated signal.

The fifth present invention provides an optical disk manufacturingapparatus, wherein the key information recording unit comprises a laserbeam generation unit for generating a laser beam, an optical intensitymodulation unit for modulating the laser beam according to the keyinformation, and a converging unit for converging and irradiating themodulated laser beam on a predetermined position on the optical disk.

The sixth present invention provides an optical disk manufacturingmethod for manufacturing an optical disk having recorded digital data tobe read out by irradiating a laser beam comprising an encryption stepfor encrypting input digital data according to a plurality of keyinformation, an optical disk substrate manufacturing step formanufacturing optical disk substrates on which the encrypted digitaldata and the key information are recorded in the form of physicalconfigurational change, a reflection film forming step for forming areflection film on the optical disk substrate, and a key informationrecording step for recording the key information on the optical disksubstrate on which the reflection film is formed.

The seventh present invention provides an optical disk manufacturingmethod, wherein the optical disk substrate manufacturing step comprisesan exposing step for converging a laser beam on an optical diskaccording to the encrypted digital data and the key information toexpose the optical master disk, a stamper forming step for forming astamper by applying a chemical treatment on the exposed optical masterdisk to change the physical configuration thereof, and a duplicationstep for transferring the physical configurational change on thestamper, thereby generating a plurality of optical disk substrates.

The eighth present invention provides an optical disk manufacturingmethod, wherein the key information recording step comprises a lasergenerating step for generating a laser beam, a modulation step formodulating the laser beam according to the key information, and a laserirradiation step for converging and irradiating the laser beam on theoptical disk substrate.

The ninth present invention provides an optical disk having digital datarecorded in the form of physical configurational change, which iscomposed so as to reproduce digital data by reflecting an incident laserbeam from its reflection film, wherein the digital signal is encryptedaccording to a plurality of key information, one of the plurality of keyinformation is recorded on the optical disk in the form of physicalconfigurational change, and at least one of the plurality of keyinformation is recorded in the form of reflectance change of thereflection film on the optical disk.

The tenth present invention provides an optical disk reproducing methodfor reproducing an optical disk having recorded encrypted digital data,wherein the method comprises the first reproducing step for reproducingthe first key information recorded on the optical disk in the form ofphysical configurational change, the second reproducing step forreproducing the second key information recorded on the optical disk inthe form of reflectance change, and a decryption step for reproducingthe digital data recorded on the optical disk and decrypting thereproduced digital data by use of the first and second key information.

In the eleventh present invention applied to an optical disk apparatusor optical disk recording method, the beam intensity of a recordinglaser beam irradiated onto an optical disk is raised intermittentlyaccording to the edge detection result and the recording signal tolocally change the reflectance of the optical disk, thereby the timingwhen the reflecting beam reception result crosses the predeterminedreference level is changed.

In the present invention applied to an optical disk, the reflectancechanges locally so that a jitter is given to the reflected beamreception result obtained by scanning the laser beam on pits or marks,and additional data is recorded according to the local reflectancechange.

The beam intensity of the recording laser beam irradiated onto theoptical disk is raised intermittently to locally change the reflectanceof the optical disk and the timing when the reflected beam receptionresult crosses the predetermined reference level is changed, thereby theadditional data is reproduced so that the optical disk is not copiedillegally, the additional data such as disk discrimination code isrecorded, and the additional data is reproduced by processing thereproduction signal for reproduction without any adverse effect on thereproduction of the data recorded in the form of pit or mark pattern.

In the present invention applied to an optical disk, the reflectance islocally changed so as to give a jitter to the reflected beam receptionresult obtained by scanning a laser beam on pits or marks, and theadditional data is recorded according to the local reflectance change,thereby the additional data is reproduced so that the optical disk isnot copied illegally, the additional data such as disk discriminationcode is recorded, and the additional data is reproduced by processingthe reproduction signal for reproduction without any adverse effect onthe reproduction of the data recorded in the form of pit or markpattern.

Furthermore, according to another present invention when applied to anoptical disk apparatus or an optical disk recording method, the mainmodulation signal is generated according to the main data, and the laserbeam is irradiated on the optical disk according to this main modulationsignal, thereby forming a pit string or a mark string thereon andsub-data is generated according to the sub-data, thereby generating thesub-modulation signal and the irradiation point of the laser beam isdeviated towards the inner/outer region of the optical disk according tothis sub-modulation signal.

Furthermore, according to the present invention when applied to anoptical disk, if the main data is recorded according to the length of apit or mark and the interval between pits or marks along the track, thensub-data is recorded according to the deviation of the pit or marktowards the inner/outer region from the center of the track.

Furthermore, according to the present invention when applied to anoptical disk apparatus, the deviation detection signal is output, thenprocessed with reference to the reproduction signal, thereby reproducingthe sub-data recorded in the form of a deviation of the pit or marktowards the inner/reference region of the optical disk with reference tothe center of the track. The signal level of the deviation detectionsignal is changed according to the deviation of a pit or mark towardsthe inner/outer region of the optical disk from the center of the track.

According to the present invention when applied to an optical diskreproducing method, the main data recorded in the form of a pit stringor a mark string is reproduced with the reflected beam of the laser beamirradiated on the optical disk and the recorded sub-data is reproducedin the form of a deviation of the pit or mark towards the inner/outerregion from the center of the track with the same reflected laser beam.

According to a configuration of an optical disk apparatus, if the mainmodulation signal is generated according to the main data and a pitstring or a mark string is formed with the laser beam irradiatedaccording to this main modulation signal, and the sub-modulation signalis generated according to sub-data and the irradiation point of thelaser beam is deviated according to this sub-modulation signal towardsthe inner/outer region of the optical disk, then the sub-data can berecorded with the selection of this deviation in the inner/outer regionso as not to disturb the reproduction of the main data recorded in theform of pits or marks. The sub-data can also be recorded so as to beprevented from illegal copying and reproduced with an optical pickup forreproducing the main data together with the assignment of various datafor inhibiting illegal copying, etc.

According to a configuration of an optical disk if the main data isrecorded according to the length of a pit or a mark and the intervalbetween pits or marks along the track and sub-data is recorded in theform of a deviation of pits or marks towards the inner/outer region ofthe optical disk with reference to the center of the track, then themain data can be reproduced correctly with the selection of thisdeviation of the pit or mark towards the inner/outer region of theoptical disk. In addition, the sub-data can be recorded so as to bedifficult to copy illegally and to be reproduced with an optical pickupfor reproducing the main data together with the assignment of variousdata for inhibiting illegal copying, etc.

Furthermore, according to a configuration of an optical disk reproducingapparatus, if the deviation detection signal is output and processedwith reference to the reproduction signal, thereby the recorded sub-datais reproduced according to the deviation of the pit or mark to theinner/outer region of the optical disk with reference to the center ofthe track, the main data recorded as a pit string or mark string can bereproduced from an optical disk composed as described above, as well asthe sub-data recorded in the form of a deviation of pits or markstowards the inner/outer region of the optical disk can be reproducedfrom the same optical disk. The level of the deviation detection signalis changed according to the deviation of the pit or mark towards theinner/outer region of the optical disk with reference to the center ofthe track.

Furthermore, according to a configuration of an optical disk reproducingmethod, if the main data recorded in the form of a pit string or a markstring is reproduced with the reflected beam of the laser beamirradiated on the optical disk and the sub-data recorded in the form ofa deviation of pits or marks towards the inner/outer region of theoptical disk with reference to the center of the track is reproducedwith the same reflected beam of the laser beam, then both main andsub-data can be reproduced from an optical disk having various recordeddata for inhibiting illegal copying so as to be reproduced with anoptical pickup for reproducing data recorded in the form of a pitstring, etc. and to be difficult to copy illegally.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram for an example of an apparatus formanufacturing optical disks in accordance with an embodiment of thepresent invention.

FIG. 2 is a block diagram for a cutting machine provided for theapparatus for manufacturing optical disks shown in FIG. 1.

FIGS. 3A to 3D are diagrams for an example of an optical disk inaccordance with an embodiment of the present invention; A is aperspective view of the optical disk, B is a diagram for the lead-inarea, C is a diagram for the data area, and D is a diagram for thelead-out area.

FIG. 4 is a block diagram for an example of a reproducing apparatus forreproducing an optical disk in accordance with the embodiment of thepresent invention.

FIG. 5 is a flow chart for the operation of a system controller providedfor the reproducing apparatus for reproducing the optical disk shown inFIG. 4.

FIG. 6 is a block diagram for an optical disk apparatus used forprocessing a compact disk in accordance with an embodiment of thepresent invention.

FIGS. 7A to 7E are a cross sectional view and a timing chart for acompact disk which is processed by the optical disk apparatus shown inFIG. 6.

FIGS. 8A-1 to 8J-2 are a timing chart for the operation of the opticaldisk shown in FIG. 6.

FIG. 9 is a block diagram for a delay circuit, an edge detectioncircuit, and a modulation circuit of the optical disk apparatus shown inFIG. 6.

FIG. 10 is a block diagram for a compact disk player for reproducing acompact disk recorded by the use of the optical disk apparatus shown inFIG. 6.

FIG. 11 is a block diagram for a disk discrimination code reproducingcircuit of the compact disk player shown in FIG. 10.

FIG. 12 is a block diagram of an optical disk apparatus used forcreating an optical disk in accordance with an embodiment of the presentinvention.

FIG. 13 is a block diagram of a key modulation circuit provided for theoptical disk apparatus shown in FIG. 12.

FIG. 14A through 14E-2 are timing charts for the operation of the keymodulation circuit shown in FIG. 13.

FIG. 15 is a block diagram of an optical disk apparatus for reproducingdata from an optical disk created with the use of the optical diskapparatus shown in FIG. 12.

FIG. 16 is a block diagram of a key modulation circuit provided for theoptical disk apparatus shown in FIG. 15.

FIGS. 17A1 through 17D are timing charts for the operation of the keymodulation circuit shown in FIG. 16.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1—1) Configuration in an Embodiment

Hereunder, an apparatus and a method for manufacturing optical disks,and an optical disk in accordance with an embodiment of the presentinvention will be described in detail with reference to the accompanyingdrawings.

First, an apparatus and a method for manufacturing an optical disks inaccordance with an embodiment of the present invention will be describedwith reference to FIG. 1. The apparatus for manufacturing optical disksin this embodiment is an apparatus for manufacturing compact disks (CD).In FIG. 1, the digital audio signal SA reproduced from a magnetic tapeby a digital tape recorder 21 is supplied to the first encryptioncircuit 22, and encrypted according to a first key information signalKY1 supplied from the first key information generation circuit 24. Theencrypted digital audio signal SB supplied from the first encryptioncircuit 22 is supplied to the second encryption circuit 23 and encryptedaccording to a second key information signal supplied from the secondkey information generation circuit 25. The double-encrypted digitalaudio signal SC supplied from the second encryption circuit 23 and thesecond key information signal KY2 supplied from the second keyinformation generation circuit 25 are supplied to an disk substratemanufacturing unit 2, and a disk substrate on which the double-encrypteddigital audio signal SC and the second key information signal KY2 arerecorded in the form of convex-concave pits is manufactured.

In the cutting machine 3 provided for the disk substrate manufacturingunit 2, a laser beam is modulated by the use of the double-encryptedaudio signal SC supplied from the second encryption circuit 23 and thesecond key information signal KY2 supplied from the second keyinformation generation circuit 23, and a master disk 26 is exposed tothe modulated laser beam.

The exposed master disk 26 is subjected to developing process andplating process through a developing and plating unit 27, therebyobtaining a stamper 28. The stamper 28 is set on an injection moldingmachine 29, and a disk substrate 4 formed of plastic material such aspolycarbonate is molded by the injection molding machine 29. On the disksubstrate 4 formed as described above, the double-encrypted digitalaudio signal SC and the key information signal KY2 are recorded in theform of very small convex-concave (pit).

Next, a reflection film is formed on the disk substrate 4 by thereflection film forming unit 41, thereby obtaining a half-finished disk5. On the half-finished disk 5, the double-encrypted digital audiosignal SC and the second key information signal KY2 supplied form thesecond key information generation circuit 25 are recorded in the form ofconcave-convex pit, and the reflection film for reflecting a laser beamis formed on the opposite side of the pit. However, the first keyinformation signal KY1 generated from the first key informationgeneration circuit 24 is not recorded on the half-finished disk 5.Accordingly, it is impossible to reproduce the recorded music becausethe encryption by the first encryption circuit 22 cannot be decrypted asis when the half-finished disk 5 is loaded into an optical disk player.

Finally, the half-finished disk 5 is loaded into a CD-R recording unit7. In the CD-R recording unit 7, the first key information signal KY1supplied from the first key information generation circuit 24 issupplied to a computer 6, the area (lead-out area) where the user datais not recorded receives an access in response to a command from thecomputer 6, and the first key information signal KY1 supplied from thefirst key information generation circuit 24 is recorded additionally.The information signal recorded additionally by the CD-R recording unit7 is recorded in the form of reflectance change of the reflection filmformed by the reflection film forming unit.

On the compact disk (completed disk) 8 completed as described above, thesecond key information signal KY2 from the second key informationgeneration circuit 25 and the first key information signal KY1 from thefirst key information generation circuit 24 are recorded in addition tothe reproduced digital audio signal SA obtained from the digital taperecorder 21. When music data or the like recorded on the compact disk 8is reproduced by an optical disk reproducing apparatus describedhereinafter, it is possible to obtain the first key information signalKY1 and the second key information signal KY2 from the compact disk 8,the double encryption can be decrypted, and a user can enjoy the musicin the same manner as in the case of a conventional compact disk.

The first encryption circuit 22 encrypts the digital audio signal SAaccording to the first key information signal KY1 generated from thefirst key information generation circuit 24 according to a DES code, andgenerates it as an encrypted digital audio signal SB. By the way, theDES code is the abbreviation of Data Encryption Standard. It is anencryption method which is used widely. Similarly, the second encryptioncircuit 23 encrypts the encrypted digital audio signal SB according tothe second key information signal KY2 generated from the second keyinformation generation circuit 25 according to the DES code, andgenerates it as a double-encrypted digital audio signal SC.

The first key information generation circuit 24 and the second keyinformation generation circuit 25 generate the first key informationsignal KY1 and the second key information signal KY2 each time a newdisk is cut. It has been known that a circuit for generating such a keyinformation signal is composed of, for example, an LFSR (Linear FeedbackShift Register).

Next, the configuration of the cutting machine 3 shown in FIG. 1 will bedescribed with reference to FIG. 2. The cutting machine 3 is used forrecording the double-encrypted digital audio signal SC and the secondkey information signal KY2 on the master disk 26 with the laser beamexposed as described above. A modulation circuit 31 processes thedouble-encrypted digital audio signal SC in the data process specifiedfor the compact disk, thereby generating an EFM signal SD and outputs itto an optical modulator 35. Further in detail, the double-encrypteddigital audio signal SC is added with an error correction signal, andthen subjected to interleave process and then to EFM modulation so as togenerate an EFM signal SD. The modulation circuit 31 inserts subcodedata including TOC (Table of Contents) supplied from a subcode generatornot shown in the drawing in the subcode area of the EFM signal SD.

The modulation circuit 32 FM-modulates the second key information signalKY2 and outputs it to the optical modulator 34 as an analog wave keyinformation modulation signal KYD. The FM modulation involves the sameprinciple as used for recording the address information of an opticaldisk, for example, an MD (mini disk), and the detailed description isomitted. In the FM modulation, a clock signal or the like is embedded sothat, for example, the key information signal KY2 is restored from thekey information modulation signal KYD.

The modulation circuit 32 is set by a system controller not shown in thedrawing so as to be operated only while the cutting machine 3 isoperated for recording on the lead-in area. Therefore, the keyinformation modulation signal KYD remains at a constant voltage and thesignal is not modulated by the optical modulator 34 during the timeperiod while the cutting machine 3 is cutting both data area andlead-out area.

The master disk 26 is rotated by a spindle motor 38. The spindle motoris controlled by the spindle servo circuit 39. Actually, the FG signalwhose signal level rises is output at each predetermined rotation angle.The FG signal is output by an FG signal generator (not illustrated)provided on the bottom of the spindle motor 38. The spindle servocircuit 39 drives the spindle motor 38 so that the frequency of the FGsignal is adjusted to a predetermined frequency. As described above, themaster disk 26 is rotated at a predetermined rotation speed.

A recording laser source 33 emits a laser beam L1 to the opticalmodulator 34 and the optical modulator 35. The recording laser source 33comprises, for example, a gas laser. The optical modulator 34 and theoptical modulator 35 comprise an electro-acoustic-optical element or thelike. The optical modulator 34 changes the traveling direction of thelaser beam emitted from the recording laser source 33 according to thekey information modulation signal KYD supplied from the modulationcircuit 32. In other words, the optical modulator 34 irradiates thelaser beam L2 whose emission angle is changed slightly according to thelevel of the key information modulation signal KYD. Such modulation ofthe emission angle of the laser beam is used as an AOD (Acoustic OpticalDeflector) generally.

The laser beam L2 traveling in the direction which is changed by the keyinformation modulation signal KYD is applied into the optical modulator35 and ON/OFF-controlled by the optical modulator 35 correspondingly tothe EFM (Eight to Fourteen Modulation) signal SD supplied from themodulation circuit 31, and emitted as a laser beam L3.

The mirror 36 reflects the laser beam L3 in the direction of the opticalpath which is reflected at an angle of, for example, 90 degrees towardthe master disk 26. An objective lens 37 converges the reflected beamfrom the mirror 36 on the recording side of the master disk 26. Thetraveling direction change (corresponding to the key informationmodulation signal KYD) of the laser beam L3 reflected on the mirror 36is recorded on the disk in the form of positional deviation of theconverged beam spot.

The mirror 36 and the objective lens 37 are moved step by step by athread mechanism (not illustrated) in the radial direction synchronouslywith the rotation of the master disk 26. As described above, theconvergent position of the laser beam L3 is moved step by step, forexample, from the inner region toward the outer region of the masterdisk 2, thereby forming a spiral track on the master disk 26. The pitsare formed successively on the track corresponding to the EFM signal SD.Because the traveling direction of the laser beams L2 and L3 ismodulated by the optical modulator 34 as described above, the centralposition of the pit string formed on the lead-in area is deviated in thetransverse direction with respect to the track correspondingly to thekey information modulation signal KYD.

The master disk 26 is exposed to the laser beam L3 modulated accordingto the double-encrypted digital audio signal SC and the second keyinformation signal KY2.

The exposed master disk 26 is subjected to developing and platingprocess as described in FIG. 1, thereby forming a stamper 28. Thestamper 28 is set on the injection molding machine 29 to form a disksubstrate 4 formed of such a plastic material as polycarbonate. Thereflection film is formed on the disk substrate 4, thereby forming ahalf-finished disk 5. Finally, the half-finished disk 5 is loaded in aCD-R recording unit 7. In the CD-R recording unit 7, the area where theuser data is not recorded (lead-out area) is accessed in response to acommand from the computer 6, and the first key information signal KY1from the first key information generation circuit 24 is additionallyrecorded. The information which is additionally recorded in the CD-Rrecording unit is recorded in the form of reflectance change of thereflection film formed by the reflection film forming machine 41.

Basically, the CD-R recording unit 7 has the same structure as that ofthe commercially available CD-R unit excepting that the CD-R unit ismodified so that the lead-out area is accessed.

A compact disk 8 completed as described above (finished disk) is shownschematically in FIG. 3A. As shown in FIG. 3A, the compact disk 8 isdivided into 3 areas. The innermost circumference side is the lead-inarea (lead-in) LI, the intermediate area is the data area DA, and theoutermost area is the lead-out area (lead-out) LO.

On the lead-in area LI, the TOC information and the second keyinformation signal KY2 used for accessing the compact disk 8 arerecorded. An example of a schematic picture obtained when the lead-inarea is observed by a microscope is shown in FIG. 3B whose TOCinformation is recorded in the form of pits. The central position ofeach of such pits is deviated slightly from the center of the track, thesecond key information signal KY2 is recorded in the form of deviation.

The data area DA is an area where the double-encrypted digital audiosignal SC is recorded. When this area is observed by a microscope, it isfound that the double-encrypted digital audio signal SC is recorded inthe form of pits, for example, as shown in FIG. 3C. Because the secondkey information signal KY2 is not recorded on the data area, the centralposition of each pit is not deviated.

On the lead-out area LO, the key information KY1 is recorded by the CD-Rrecording unit 7. When this area is observed by a microscope, it isfound that the first key information signal KY1 is recorded in the formof reflectance change as shown, for example, in FIG. 3D. It isunderstood that the information is recorded not as a physical change(concave-convex).

For example, it is assumed that a pirated disk maker get a compact disk8 manufactured as described above and tries to make a pirated disk bysupplying the reproduced signal obtained from the compact disk 8 to acutting machine. As a result, the TOC information recorded on thelead-in LI, the information of the data area, and the information of thelead-out are all supplied to the cutting machine, and recorded on thepirated disk. However, the second key information signal KY2 recorded inthe form of positional deviation of each pit on the lead-in LI does notappear in the reproduced signal, thus not recorded in the pirated disk.Because the second key information signal KY2 cannot be decrypted by theuse of the pirated disk made in the manner as described above, it isimpossible to reproduce the music signal or the like. Accordingly, thepirated disk is useless, and making of such pirated disks by the use ofthe method as described above is prevented.

Next, it is assumed that a pirated disk maker gets a compact disk 8 andtries to make a pirated disk by the use of a method in which the pitsare transferred physically. In this case, it is likely that the secondkey information signal KY2 recorded in the form of positional deviationon the lead-in area is transferred onto the pirated disk as is. However,the first key information signal KY1 recorded on the lead-out LO area isrecorded in the form of reflectance change, and does not cause physicalconvex-concave. Therefore, the first key information signal KY1 is nottransferred onto the pirated disk. Because the encryption by the firstkey information signal KY1 cannot be decrypted by the use of the pirateddisk made as described above, therefore, it is impossible to reproduceit. And accordingly, the pirated disk is useless, so that making of suchpirated disks by the use of the method as described above is prevented.

As described above, according to the example in accordance with theembodiment of the present invention, it is possible to prevent thepirated disk making by the use of any of the methods in which a disk isphysically transferred and the method in which the reproduced signal issupplied directly to a cutting machine.

Next, a reproducing apparatus 50 for reproducing a compact disk 8manufactured as described above will be described with reference to FIG.4.

The reproducing apparatus 50 shown in FIG. 4 is controlled by a systemcontroller 64. The compact disk 8 is rotated by a spindle motor 51. Thespindle motor 51 and an optical pickup 53 are controlled by servocircuit 52 so as to perform a predetermined operation. A reproduced RFsignal generated from the optical pickup 53 is supplied to a binarycircuit 54. A push-pull signal PP supplied from the optical pickup 53 issupplied to an A/D converter 61.

The binarization circuit 54 compares the supplied reproduced RF signalwith a predetermined slice level, thereby generating a binary signal.The binary signal is supplied to an EFM demodulation circuit 55. The EFMdemodulation circuit 55 demodulates EFM from the binary signal, therebygenerating an 8 bit-signal, and supplies the generated 8 bit-signal toan ECC (error correction circuit) circuit 56.

The ECC circuit 56 corrects errors in the output of the EFM demodulationcircuit 55 according to the ECC (Error Correcting Code) added duringcoding in recording. Such an error is caused, for example, from a defecton the compact disk 8.

On the other hand, the A/D converter 61 digitizes (quantization) thepush-pull signal and supplies it to a DSP 62 as a digital reproducedsignal DRF. Because the push-pull signal PP is a signal which isproportional to the positional deviation of the pit from the trackcenter, the push-pull signal includes the information recorded as thesecond key information signal KY2. The DSP 62, which is a digital signalprocessing processor, processes the digital reproduced signal DRFaccording to a program recorded in the internal portion and demodulatesFM modulation modulated by the modulation circuit 32, thereby findingthe second key information signal KY2.

A first cryptogram processing circuit 57 decrypts the encryption appliedto the output signal from the ECC circuit 156 by the use of the secondkey information signal KY2 determined as described above. Theinformation from which the second encryption (encrypted by the secondencryption circuit 23 shown in FIG. 1) is decrypted is suppliedsubsequently to the second encryption processing circuit 58.Simultaneously, the signal from the ECC circuit 56 is supplied also to amemory 63. A system controller 64 controls the memory 63 to store thefirst key information signal KY1 in the memory 63. Consequently, thefirst key information signal KY1 stored in the memory 63 is keptsupplied to the second cryptogram processing circuit 58, thus the secondcryptogram processing circuit 58 can decrypt the first encryption(encrypted by the first encryption circuit 22 shown in FIG. 1).

Because the encryption is decrypted as described above, the digitalaudio signal SA is restored on the output side of the second cryptogramprocessing circuit 58. The digital audio signal SA obtained as describedabove is converted to an analog audio signal by a D/A converter 59 andsent to an output terminal 60, and supplied to a speaker or the like forsounding.

The decryption operation as described above is performed by the systemcontroller 64. The system controller 64 is composed so that apredetermined operation shown by a flow chart in FIG. 5 is performed bythe reproducing apparatus 50 each time a new optical disk 8 is loaded,thereby realizing the decryption process as described aboveconsistently.

In the process performed by the system controller 64 shown in FIG. 5,first the system controller 64 gives a command to respective componentsof the system including the servo circuit 52 in step ST-1 and instructsfor the movement of the focal point of the beam emitted from the opticalpickup to the lead-in area LI of the optical disk 8. Next, in step ST-2,the push-pull signal PP supplied from the optical pickup 53 is quantizedby the A/D converter 61, and processed by the DSP 62, thereby decodingthe information recorded as the second key information signal KY2. Next,in step ST-3, the decoded second key information signal KY2 is suppliedto the output terminal of the DSP 62, and the value is retained.

The system controller 64 instructs for the movement of the focal pointof the beam emitted from the optical pickup to the lead-out area LO instep ST-4. Next, in step ST-5, the system controller 64 instructs forstoring of the read-out first key information signal KY1 in the memory63. As described above, the first key information signal KY1 and thesecond key information signal KY2 are obtained, and then the systemcontroller 64 controls the whole system so as to reproduce the data fromthe compact disk 8 for sounding.

As described above, the system controller 64 controls the whole systemso that the key information recorded on the lead-in area LI and lead-outarea LO is read out and the decryption of cryptogram is performed andthe sound is generated after that. Consequently, it is prevented thatthe encryption is not decrypted while a large noise is generated as asound from the speaker.

In the case that the compact disk 8 is a normal disk (not a pirateddisk), both first and second key information signals KY1 and KY2 aredecoded correctly. Consequently, the first and second cryptogramprocessing circuits 57 and 58 can obtain the information required fordecryption. Therefore, the output of the second cryptogram processingcircuit 58 is supplied to the D/A converter 59, the output of the D/Aconverter 59 is converted to, for example, a music signal, and thus thesubject user can enjoy the music recorded in the compact disk 8.

In the case that a disk obtained by the apparatus for manufacturingoptical disks of the present invention is reproduced and the reproducedsignal is supplied again to a cutting machine to make a pirated disk,the pirated disk has no second key information signal KY2 recorded inthe form of positional deviation of the pit. Therefore, when the pirateddisk is tried to be reproduced by the use of an optical disk reproducingapparatus shown in FIG. 4, the user can not enjoy the music from such apirated disk. In the case that a pirated disk is obtained by a method inwhich the physical configuration of a disk is transferred as describedpreviously, also the user can not enjoy the music.

In the above-mentioned example of this embodiment, although the casethat the second key information KY2 is recorded in the form ofpositional deviation of the pit is described, the present invention isnot limited only to this case; for example, the second key informationsignal KY2 may be recorded in the form of slight change of the pitwidth. In this case, an optical detection system for detecting apush-pull signal is not required for the optical disk reproducingapparatus, the structure of the optical disk reproducing apparatus issimplified and the cost is reduced.

(1-2) Effects of the Above Embodiments

According to the first to fifth present inventions, because an opticaldisk manufacturing apparatus for manufacturing an optical disk havingrecorded digital data to be read out by irradiation of a laser beamcomprises an encryption unit for encrypting input digital data accordingto a plurality of key information, an optical disk substratemanufacturing unit for manufacturing an optical disk substrate on whichthe encrypted digital data and the key information are recorded in theform of physical configurational change, a reflection film forming unitfor forming a reflection film on the optical disk substrate, and a keyinformation recording unit for recording the key information on theoptical disk substrate having the reflection film thereon, an opticaldisk manufacturing apparatus which exhibits the effect as describedherein under is obtained In detail, according to the first to fifthpresent inventions, because the key information is recorded by the useof two different methods, namely physical configurational change andreflectance change of a reflection film, an optical disk manufactured bysuch a manufacturing apparatus of the present invention can not beduplicated not only by the use of physical transfer and a pirated diskcan not be obtained but also by a method in which the reproduced signalreproduced from an optical disk manufactured by the use of themanufacturing apparatus of the present invention is supplied directly toa cutting machine Therefore, accordingly to the optical diskmanufacturing apparatus of the first to fifth present inventions, anoptical disk which protects the profit of the object rightful copyrightholder is manufactured.

According to the sixth to eighth present inventions, because an opticaldisk manufacturing method for manufacturing an optical disk having therecorded digital data to be read out by irradiating a laser beamcomprises an encryption step for encrypting input digital data accordingto a plurality of key information, an optical disk substratemanufacturing step for manufacturing an optical disk substrate on whichthe encrypted digital data and the key information are recorded in theform of physical configurational change, a reflection film forming stepfor forming a reflection film on the optical disk substrate, and a keyinformation recording step for recording the key information on theoptical disk substrate on which the reflection film is formed, anoptical disk manufacturing method which exhibits the effect as describedhereunder is obtained. In detail, according to the sixth to eighthpresent inventions, an optical disk manufactured by an optical diskmanufacturing method of the present invention can not be duplicated notonly by means of physical transfer and a pirated disk can not beobtained but also by a method in which the reproduced signal reproducedfrom an optical disk manufactured by the use of the optical diskmanufacturing method of the present invention is supplied directly to acutting machine. Therefore, accordingly to the optical diskmanufacturing method of the sixth to eighth present inventions, anoptical disk which protects the profit of the rightful copyright holderis manufactured.

According to the ninth present invention, because an optical disk hasdigital data recorded in the form of physical configurational change andreproduces the digital data by reflecting an incident laser beam fromits reflection film, wherein the digital signal is encrypted accordingto a plurality of key information, one of the plurality of keyinformation is recorded on the optical disk in the form of physicalconfigurational change, and at least one of the plurality of keyinformation is recorded in the form of reflectance change of thereflection film on the optical disk, it is possible to obtain an opticaldisk which exhibits the effect as described hereunder. In detail,according to the ninth present invention, because the digital datarecorded on an optical disk is encrypted according to a plurality of keyinformation, one of the plurality of key information is recorded in theform of physical configurational change on the optical disk and at leastone of the plurality of key information is recorded in the form ofreflectance change of a reflection film on the optical disk, the opticaldisk of the ninth present invention can not be duplicated not only bymeans of physical transfer and a pirated disk can not be obtained butalso by a method in which the reproduced signal reproduced from anoptical disk of the present invention is supplied directly to a cuttingmachine. Therefore, accordingly to the optical disk manufacturing methodof the ninth present invention, it is possible to manufacture an opticaldisk which protects the profit of a rightful copyright holder.

According to the tenth present invention, because the invention providesan optical disk reproducing method for reproducing data from an opticaldisk having digital data recorded thereon in the form of physicalconfigurational change and so as to be read out with a laser beamirradiated on its reflection film, wherein the digital data is encryptedaccording to a plurality of key information, one of the plurality of keyinformation is recorded in the form of physical configurational changeon the optical disk, and at least one of the plurality of keyinformation is recorded in the form of reflectance change of thereflection film on the optical disk, the optical disk reproducing methodwhich exhibits the effect as described herein under is obtained. Indetail, according to the tenth present invention, it is possible toobtain the optical disk reproducing method for decrypting correctly andreproducing the data recorded on a disk, even though the disk issubjected to pirated copy protection by means of encryption.

(2-1) Configuration in Another Embodiment

FIG. 6 is a block diagram for an optical disk apparatus in accordancewith an embodiment of the present invention. The optical disk apparatus1 records a disk discrimination code ED on a compact disk 2 on whichdigital audio signal is already recorded in the form of pit string in acompact disk manufacturing process.

In detail, as shown in FIG. 7, a disk substrate 3 of the compact disk 2(shown in FIG. 7D) is manufactured with such plastic as polycarbonate inthe same manner as used for manufacturing an ordinary compact disk bymeans of injection molding using a stamper. Fine convex-concaveconfiguration corresponding to pits and lands is formed on theinformation recording side of the disk substrate 3 in the injectionmolding process. As shown in an expanded view (FIG. 7E) with an arrow a,a reflection recording film 4 for reflecting a laser beam is formed onthe information recording side of the disk substrate 3 of the compactdisk 2 by means of, for example, vapor deposition, and then a protectivefilm 5 for protecting the reflection recording film 4 from corrosion isformed.

Such a subcode information absolute time for specifying an audio signalreproduction position is recorded in the form of repeated pits and landson the compact disk 2 in the same manner as used for an ordinary compactdisk, and a laser beam L is irradiated onto the reflection recordingfilm 4 through the disk substrate 3 and the reflected beam is received,thereby reproducing the audio signal or the like recorded on the compactdisk 2.

75 CD frames are assigned for each second of repeated pits and landsformed as described above (FIG. 7A) in the same manner as used for anordinal compact disk and respective 98 EFM frames are assigned to eachCD frame (FIG. 7B). Furthermore, each EFM frame is divided into 588channel clocks, and a frame sync is assigned to the first 22 channelclocks. The basic period of the pit and land configuration is 1 periodof 1 channel clock. The pit and land configuration is repeated as alength of the integral multiple of this basic period, and the frame syncis composed of a period of 11T.

In this embodiment, the reflection recording film 4 is formed so as tohave the same film structure as that of the information recording sideof a CD-R. Thereby, when a laser beam L having an intensity higher thana certain level is irradiated on the compact disk 2, the reflectance ofthe reflection recording film 4 is changed irreversibly at a positionwhere the laser beam is irradiated, and the reflectance change isdetected in the form of intensity change of the reflected beam.

In the optical disk apparatus 1 (FIG. 6), a system control circuit 10comprising a micro-computer controls the whole operation, and records adisk discrimination code ED on the compact disk 2.

In the optical disk apparatus 1, a spindle motor 11 rotates the compactdisk 2 at a constant linear speed under the control of a servo circuit12.

An optical pickup 13A detects the reproduction signal RF from thecompact disk 2 prior to an optical pickup 13B, and the optical pickup13B records the disk discrimination code ED on the compact disk 2according to the process result of the reproduction signal RF detectedby the optical pickup 13A.

In detail, the optical pickups 13A and 13B are linked by a threadmechanism in the movement in the radial direction of the compact disk 2so as to irradiate laser beams adjacently on the same track. The opticalpickups 13A and 13B are under tracking control and focus controlindependently according to the reception result of the reflected beamobtained by irradiating the laser beam on the compact disk 2, therebythe optical pickup 13B scans the same position just after the opticalpickup 13A scans.

The optical pickup 13A receives the reflected beam at a predeterminedreception element, and detects the reproduction signal RF having thesignal level which varies correspondingly to the beam intensity changeof the reflected beam on the reception face of the reception element.The optical pickup 13B raises the beam intensity of the laser beam at apredetermined timing under the control of the APC (Automatic PowerControl) circuit 14, thereby locally changing the reflectance of thereflection recording film 4 of the compact disk 2.

An amplifier circuit 15 amplifies the reproduction signal RF suppliedfrom the optical pickup 13A with a predetermined gain and sends it out.A binarization circuit 16 binarizes the reproduction signal RF suppliedfrom the amplifier circuit 15 according to a predetermined referencelevel and outputs a binary signal BD. A PLL circuit 17 reproduces achannel clock CK from the binary signal BD.

A delay circuit 22 delays the timing of the binary signal BD for a timeperiod from the time when the optical pickup 13A scans a position to thetime when the optical pickup 13B scans the same position, and outputsthe delayed timing.

A disk discrimination code generation circuit 20 comprises a subcodedetection circuit 20A and a read-only memory (ROM) 20B. The subcodedetection circuit 20A processes the binary signal DBD which is delayed apredetermined time period by the delay circuit 22, thereby reproducingsubcode information included in the binary signal DBD. Furthermore, thedisk discrimination code generation circuit 20 selectively generates thetime information of minute (AMIN) and second (ASEC) indicated by anabsolute time respectively from the minute, second, and frame includedin the subcode. At that time, the subcode detection circuit 20A alsogenerates the reset pulse which is synchronous with the second (ASEC)time information and sends it out to a conversion circuit 21.

Herein, the minute (AMIN) and second (ASEC) time information, whichindicate a data position on the compact disk 2, are the subcodeinformation specified as the standard of the compact disk 2. In otherwords, the minute (AMIN) time information represents the data recordedon the compact disk 2 in minutes and takes a value, for example, from 0to 74. The second (ASEC) time information specifies a minute-unitposition specified in minutes (AMIN) more finely in seconds, and takes avalue, for example, from 0 to 59.

The read-only memory 20B holds the disk discrimination code ED, andgenerates the data which is held according to the minute (AMIN) andsecond (ASEC) time information supplied from the subcode detectioncircuit 20A. Herein, the disk discrimination code ED includes the IDinformation which is set inherently in each disk, the information of themanufacturing factory, the data of manufacture, and the information forcontrolling permission of copying, and further includes a sync signalfor indicating the start of the disk discrimination code ED and an errorcorrection code. The read-only memory 20B holds the disk discriminationcode ED as bit data, and outputs 1 bit disk discrimination code ED tothe “1” address decided by the minute (AMIN) and second (ASEC) timeinformation. Thereby, the read-only memory 20B generates 1 bit diskdiscrimination code ED for each second.

To generate the disk discrimination code ED and output it as describedabove, in the compact disc 2, 1 second consists of 75 CD frames and 1 CDframe consists of 98 EFM frames (FIG. 8(A-1) to (A-3)) as shown incomparison between FIG. 7 and FIG. 8, the disk discrimination codegeneration circuit 20 generates 1 bit disk discrimination code ED (FIG.8D) in units of 7350 (7350=75×98) EFM frames, and sends it out. Thereby,the disk discrimination code generation circuit 20 generates and sendsout the disk discrimination code ED so that at least 10 pit edges on thecompact disk correspond to 1 bit of the disk discrimination code ED.

The conversion circuit 21 scrambles the disk discrimination code ED withreference to the sync pattern and sends it out. It is thereby difficultto find the disk discrimination code ED.

In other words, in the conversion circuit 21, a sync pattern detectioncircuit 21A detects the sync pattern which appears repeatedly in thebinary signal DBD supplied from the delay circuit 22. At that time, thesignal level of the binary signal DBD (FIG. 8A-4) is switchedcorrespondingly to a pit string formed on the compact disk 2, the signallevel rises up at the frame sync assigned to the start of each frame fora time period of 11T and then the signal level falls down for a timeperiod of 11T.

Therefore, the sync pattern detection circuit 21A determines the signallevel of the consecutive binary signal DBD with reference to the channelclock CK (FIG. 8B) by the use of multi-connected flip-flop circuits,thereby detecting the frame sync. In the present embodiment, the syncpattern detection circuit 21A generates a frame pulse FP (FIG. 8C) whosesignal level rises during a time period T, which is 1 channel clockbefore the start of the frame sync in the comparison with the timing ofthe binary signal DBD to be processed by the subcode detection circuit20A according to the detection result of the frame sync.

An M-series generation circuit 21B comprises a plurality ofcascade-connected flip-flops and exclusive OR circuits, sets the initialvalue to each of the plurality of flip-flops at a timing correspondingto the second (ASEC) time information change according to the resetpulse supplied from the subcode detection circuit 20A, and thentransfers the set content successively synchronously with the framepulse FP and feeds it back at a predetermined interstage, therebygenerating M-series random number data MS in which the logic levels 1and 0 appear at the same probability.

The exclusive OR circuit 21C receives the M-series signal MS and thedisk discrimination code ED, and generates the exclusive OR signal to beused as a conversion signal MD (FIG. 8E). In detail, the exclusive ORcircuit 21C generates a conversion signal MD according to the logicallevel of the M-series signal MS in the case that the logical level ofthe disk discrimination code ED is 0. On the other hand, the circuit 21Cgenerates a conversion signal MD having the inverted logical level ofthe M-series signal MS in the case that the logical level of the diskdiscrimination code ED is 1. Thereby, the exclusive OR circuit 21Cmodulates the disk discrimination code ED according to the M-seriesrandom number.

An edge detection circuit 23 detects the timing of each pit edge formedon the compact disk 2 according to the binary signal DBD supplied fromthe delay circuit 22 and sends it out. The modulation circuit 24 gatesthe conversion signal MD at the timing of this edge, thereby raising thecontrol signal MX for an APC circuit 14. The beam intensity of the laserbeam is thus raised in a moment, thereby changing the reflectance of thecompact disk 2 locally.

In detail, as shown in FIG. 9, the delay circuit 22 transfers the binarysignal BD synchronously with the channel clock CK successively by theuse of the predetermined stages of cascade-connected flip-flops 22A to22O, thereby delaying the binary signal BD and outputs the delayedsignal. The number of stages of the flip-flops 22A to 22O is set so thatthe delay time given to the binary signal BD due to the transfer of thebinary signal becomes equal to the time period between the time when theoptical pickup 13A scans a position and the time when the optical pickup13B scans the same position.

The edge detection circuit 23 supplies the output signal of theflip-flop 22O to the flip-flop 23A which is operated according to thechannel clock CK and supplies the input/output signal of the flip-flop23A to an AND circuit 23B. The AND circuit 23B has the one inputterminal which is set as an inverse input terminal so that the logicallevel of the output terminal is raised when the logical level of twoinput terminals is different from each other. The edge detection circuit23 detects the timing when the logical level of the binary signal BD isswitched and outputs the output signal of the AND circuit 23B which isthe detection result as an edge detection signal EP (FIG. 8F).

The modulation circuit 24 supplies the edge detection signal EP and theconversion signal MD to the AND circuit 24A, thereby gating theconversion signal MD according to the edge detection signal EP, andgenerates a conversion signal MXA (FIG. 8G) whose logical level rises atthe timing of a pit edge correspondingly to the logical level of theconversion signal MD.

A D-flip-flop 24B, which is operated according to the channel clock CK,removes gridge noise from the modulation signal MXA and outputs thenoise-removed signal MXA, and a monostable multi-vibrator (MM) 24Cshapes the pulse width of the pulse signal output from the D-flip-flop24B and outputs the modulation pulse MX (FIG. 8H).

The APC circuit 14 (FIG. 6) switches the beam intensity of the laserbeam emitted from the optical pickup 13B correspondingly to themodulation pulse MX from the beam intensity for reproduction to the beamintensity for recording. Herein, the beam intensity for recordingimplies a beam intensity which is sufficient to change the reflectanceof the reflection film 4 of the compact disk 2.

Consequently, the optical disk apparatus 1 raises the beam intensity ofthe laser beam corresponding to the disk discrimination code EDmodulated according to the random number data MS at the timing when thelaser beam emitted from the optical pickup 13B scans an edge of a pit P,forms the mark M so as to cover astride the corresponding edge toadditionally record the disk discrimination code ED (FIGS. 8I-1 and8I-2). Therefore, in the compact disk 2, in the case that the diskdiscrimination code ED is not recorded additionally, the reproductionsignal RF of the signal waveform in which the signal level crossesapproximately the average level at the timing when the edges of thesepits are scanned (FIG. 8J-1) is obtained. On the other hand, in the casethat the disk discrimination code ED is recorded additionally asdescribed above, the reproduction signal RF of the signal waveform inwhich the signal level is deviated locally for reflectance change at thetiming of scanning of a pit edge because the reflectance is locallychanged at the corresponding edge is obtained. And accordingly, thejitter increases for the reflectance change (FIGS. 8J-2). The diskdiscrimination code ED is recorded on the compact disk 2 according tothe jitter detected from the reproduction signal RF, and the diskdiscrimination code ED is reproduced with reference to the signal levelchange of the reproduction signal RF.

In the optical disk apparatus 1, the beam intensity of the laser beamwhich is raised by the APC circuit 14 is set and the pulse width of themodulation pulse MX, which controls the time period of the raised beamintensity of the laser beam, is set so that the reproduction signal RFis processed with the same reliability as that of the conventionalreproduction for generating the audio signal even though the signalwaveform of the reproduction signal RF is changed as described above, inother words, so that the reproduction signal RF is binary-discriminatedwith sufficient margins in phase and amplitude, thereby generating achannel clock CK correctly.

FIG. 10 is a block diagram for a compact disk player for reproducing thecompact disk 2. In the compact disk player 30, a spindle motor 32rotates the compact disk 2 at a constant linear speed under the controlof a servo circuit 33.

An optical pickup 34 irradiates a laser beam onto the compact disk 2 andreceives the reflected beam at a predetermined reception element, thengenerates a reproduction signal RF whose signal level is changedcorrespondingly to the beam intensity of the reflected beam at thereception area of the reception element. The signal level of thereproduction signal RF changes correspondingly to each pit recorded onthe compact disk 2. At that time, the reflectance of the compact disk 2is locally changed correspondingly to each pit edge according to therecorded disk discrimination code ED, and the signal level of thereproduction signal RF is thereby changed slightly correspondingly tothe reflectance change due to the disk discrimination code ED.

A binarization circuit 35 binarizes the reproduction signal RF withreference to a predetermined reference level, thereby generating abinary signal BD.

A PLL circuit 36 is operated with reference to the binary signal BD,thereby reproducing a channel clock CCK of the reproduction signal RF.

An EFM demodulation circuit 37 successively latches the binary signal BDwith reference to the channel clock CCK, thereby reproducing the datacorresponding to the EFM modulation signal S2. Furthermore, the EFMdemodulation circuit 37 EFM-demodulates the reproduction data and thendivides the demodulated data into 8-bit segments with reference to theframe sync, and deinterleaves each generated 8-bit signal and outputs itto an ECC (Error Correcting Code) circuit 38.

The ECC circuit 38 subjects the output data to an error correctionprocess according to the error correction code added to the output dataof the EFM demodulation circuit 37, thereby reproducing and outputtingthe audio data D1.

A digital analog conversion circuit (D/A) 39 subjects the audio data D1output from the ECC circuit to digital analog conversion process andoutput the analog audio signal S4. At that time, the digital analogconversion circuit 39 stops the output of the audio signal S4 when thecompact disk 2 is determined to be a compact disk copied illegally underthe control of a system control circuit 40.

The system control circuit 40 comprises a computer for controlling theoperation of the compact disk player 30. The system control circuit 40determines whether or not the compact disk 2 is an illegally copied diskaccording to the disk discrimination code ED supplied from the diskdiscrimination code reproducing circuit 41, and if the compact disk isdetermined to be an illegally copied disk, then the system controlcircuit 40 controls the digital analog conversion circuit 39 so as tostop the output of the audio signal S4.

The disk discrimination code reproducing circuit 41 decodes the diskdiscrimination code ED from the reproduction signal RF and sends it out.

FIG. 11 is a detailed block diagram for the disk discrimination codereproducing circuit 41. In the disk discrimination code reproducingcircuit 41, a subcode detection circuit 42 monitors the binary signal BDwith reference to the channel clock CCK and decodes the subcodeinformation from the binary signal BD. The subcode detection circuit 42monitors the time information included in the decoded subcode, andgenerates 1 second detection pulse SECP whose signal level rises eachtime the time information changes for 1 second.

An edge detection circuit 44 has the same structure as that of the edgedetection circuit 23 described above with reference to FIG. 9, anddetects a changing point of each pit from the binary signal BD andgenerates an edge detection signal EP.

A sync pattern detection circuit 45 successively latches the binarysignal BD with reference to the channel clock CCK, and discriminates thecontinuous logical level, thereby detecting the sync pattern andgenerating a frame pulse FP.

An M-series generation circuit 46 initializes a read-only memory addresswith reference to the 1 second detection pulse SECP, and then accessesthe built-in read-only memory by advancing the addresses one by oneaccording to the frame pulse FP, thereby generating M-series randomnumber data MZ corresponding to the M-series random number data MSgenerated by the optical disk apparatus 1.

Consequently, in the disk discrimination code reproducing circuit 41,various reference signals required to reproduce the disk discriminationcode ED are generated correspondingly to the process in the optical diskapparatus 1.

In the disk discrimination code reproducing circuit 41, the reproductionsignal RF is subjected to analog digital conversion process withreference to the channel clock CCK in the analog digital conversioncircuit 47, and an 8-bit digital reproduction signal is generated. Apolarity inverting circuit (−1) 48 inverts the polarity of the digitalreproduction signal and outputs the polarity-inverted signal.

A selector 49 selects and outputs the digital reproduction signalsupplied directly from the analog digital conversion circuit 47 and thedigital reproduction signal whose polarity is inverted, then the signalis supplied from the polarity inverting circuit 48 correspondingly tothe logical level of the M-series random number data MZ supplied fromthe M-series generation circuit 46. In detail, the selector 49 selectsand outputs the digital reproduction signal supplied directly if thelogical level of the M-series random number data MZ is 1. On the otherhand, the selector 40 selects the digital reproduction signal having theinverted polarity if the logical level of the M-series random numberdata MZ is 0. The selector 47 thus reproduces the logical level of thedisk discrimination code ED modulated with the M-series random numberdata MS according to multi-value data, thereby generating thereproduction data RX of the multi-value data.

An adder 52, which is a 16-bit digital adder, adds up the reproductiondata RX and the output data AX from an accumulator (ACU) 53 and outputsthe total. The accumulator 53 comprises a 16-bit memory for holding theoutput data of the adder 52, and composes an accumulation adder togetherwith the adder 52 because the held data is fed back to the adder 52. Indetail, the accumulator 53 clears the held data with the 1 seconddetection pulse SECP, and then records the output data from the adder 52synchronously with the output signal EP from the edge detection circuit44. Thus, the adder 52 accumulates the logical value corresponding to apit edge selected from among the logical values of the reproduction dataRX reproduced by the selector 49 every second (7350 frames) of the timeinformation set in the subcode information, thereby generating anaccumulated value AX.

A binarization circuit 54 binarizes the output data AX from theaccumulator 53 according to a predetermined reference value at thetiming when the 1 second detection pulse SECP rises, and outputs thebinary data. The reproduction data RX of the disk discrimination code EDreproduced by the selector 49 is thus converted to a binary diskdiscrimination code ED.

The disk discrimination code ED is subjected to error correction processin an ECC circuit by the use of the error correction code added to thedisk discrimination code ED, so that the error corrected code is output.

(2—2) The Operation of Another Embodiment

By applying the configuration described above, in the manufacturingprocess of a compact disk 2 in accordance with the present embodiment, amother disk is formed by an ordinary mastering apparatus, and a disksubstrate 3 is manufactured by the use of a stamper manufactured fromthe mother disk. Furthermore, a reflection recording film 4 and aprotective film 5 are formed additionally on the disk substrate 3,thereby manufacturing a compact disk 2 (FIG. 7). Pits and lands having alength of an integral multiple of the basic length corresponding to thepredetermined basic period T respectively are repeated, and the digitalaudio signal or the like is recorded on the compact disk 2.

Herein, the compact disk 2 has a reflection recording film 4 having thesame film structure as an information recording film of a CD-R, when alaser beam L having the beam intensity higher than a predetermined valueis irradiated onto the compact disk 2, the reflectance of the reflectionrecording film 4 is changed irreversibly at a position where the laserbeam is irradiated, and the subdata is recorded in addition to the maindata which is recorded in the form of repeated pits and lands.

In the optical disk apparatus 1 (FIG. 6), the disk discrimination codeED is recorded on the compact disk manufactured as described above sothat the disk discrimination code ED does not affect adversely thereproduction of the digital audio signal recorded in the form ofrepeated pits and lands.

In detail, in the optical disk apparatus 1, the reproduction signal RFobtained from the optical pickup 13A is converted to the binary signalBD by the binarization circuit 16, the channel clock CK is reproducedfrom the binary signal BD by the PLL circuit 17, and the binary signalBD is delayed by the delay circuit 22 according to a time differencebetween the time when the optical pickup 13A scans a position and thetime when the optical pickup 13B used for recording the diskdiscrimination code ED scans the same position.

In the optical disk apparatus 1, the subcode is detected by the subcodedetection circuit 20A from the binary signal DBD supplied from the delaycircuit 22, and the disk discrimination code ED is generated at anextremely low bit rate (as low as 1 bit per 1 second) synchronously withthe subcode by the access to the read-only memory 20B according to theminute (AMIN) and second (ASEC) information included in the subcode.

Simultaneously, in the sync pattern detection circuit 21A, the syncpattern is detected from the binary signal DBD, and the M-series randomnumber data MS in which logical levels 1 and 0 appear at the sameprobability at the timing synchronous with the sync pattern is generatedaccording to the detection pattern of the sync pattern in the M-seriesgeneration circuit 21B.

Also in the optical disk apparatus 1, the exclusive OR circuit 21Cmodulates the disk discrimination code ED according to the M-seriesrandom number data MS, thereby rendering the disk discrimination code EDdifficult to be found.

Also in the optical disk apparatus 1, the edge detection circuit 23(FIG. 9) detects the timing when the optical pickup 13B crosses the edgeof a pit, and the subsequent modulation circuit 24 gates the outputsignal from the exclusive OR circuit 21C with reference to the timingdetection result and shapes the output signal into a pulse obtained asthe gating result and having a narrow width, and the conversion signalMD obtained thereby raises the beam intensity of the laser beam emittedfrom the optical pickup 13B intermittently.

Consequently, the reflectance of the reflection recording film 4 of thecompact disk 2 is changed locally at a position (FIG. 8) correspondingto the rise of the beam intensity of the laser beam according to thecontrol signal MX. At that time, the output signal from the exclusive ORcircuit 21C is gated at the timing when the optical pickup 13B scans theedge of a pit, thereby raising the beam intensity of the laser beam, andthe mark M is thereby formed corresponding to the output signal of theexclusive OR circuit 21C so as to cover astride the edge of each pit.

In the compact disk 2 on which the mark M is formed as described above,although the jitter of the reproduction signal RF increases, because thereflectance change introduced as described above is very slight, thereflectance change does not affect the reproduction of the informationrecorded in the form of pit string adversely, and the clock is generatedstably and accurately and the recorded data is reproduced correctly.

In the case of the compact disk 2, because the disk discrimination codeED is disturbed by the use of the M-series in which logical levels 1 and0 appear at the same probability in the exclusive OR circuit 21C, andthe disturbed disk discrimination cod ED is recorded, when the signalwaveform of the reproduction signal RF is observed on an oscilloscope,the information of the disk discrimination code ED appears as a noiseand the disk discrimination code ED is rendered difficult to be found.Furthermore, the disk discrimination code ED is difficult to be copied.

In addition to the above, because 1 bit of the disk discrimination codeED is assigned to 1 second time period, that is, because 1 bit isrecorded dispersedly on the total 7350 (7350=75×98) EFM frames, the diskdiscrimination code ED is reproduced consistently even if thereproduction signal is disturbed due to a noise.

Although the digital audio signal D1 recorded in the form of pit stringon the compact disk 2, on which the disk discrimination is also recordedas described above, is copied by the use of the conventional illegalcopying method, the disk discrimination code ED cannot be copied.

To make exactly the same illegally copied disk as the compact disk 2, itis required to record the disk discrimination code ED in the same formof mark, and to do that a disk recording medium having a reflectionrecording film on which the digital audio signal D1 is recordedpreviously in the form of pit string must be used. Furthermore a unithaving the same structure as that of the optical disk apparatus 1 mustbe used. As a result, the disk discrimination code ED is rendereddifficult to be copied.

When the laser beam is irradiated onto the compact disk 2 (FIG. 10)manufactured as described above, in the compact disk player 30, thereproduction signal RF whose signal level is changed with timecorresponding to the beam intensity of the reflected beam obtained byirradiating the laser beam onto the compact disk 2 is detected, therebythe signal level of the reproduction signal RF changes with timecorresponding to the pit and land configuration and also correspondingto the reflectance of the compact disk 2, thereby the reproductionsignal RF is binarized by the binarization circuit 35. Subsequently, thebinary signal BD is binary-discriminated by the EFM demodulation circuit37, and then subjected to EFM demodulation and interleave process and toerror correction process carried out by the ECC circuit 38. Andaccordingly, the digital audio signal is reproduced.

At that time, although the signal level near each pit edge changesslightly due to the existence of the mark because the mark is formed bylocally changing the reflectance on the compact disk 2, the binarysignal is correctly discriminated at a sufficiently practical accuratelevel to generate a clock and reproduced correctly due to the generatedclock. Consequently, the compact disk 2 is reproduced correctly by theuse of an ordinary compact disk player even when the disk discriminationcode ED is recorded on this compact disk 2.

When in reproduction of the digital audio signal as described above, thedisk discrimination code reproducing circuit 41 reproduces the diskdiscrimination code ED simultaneously from the compact disk 2. If thedisk discrimination code ED is not reproduced correctly, then the diskis regarded as an illegally copied disk and the digital analogconversion circuit 39 is controlled to stop the digital analogconversion process immediately.

In detail, when in reproduction of the disk discrimination code ED (FIG.11) recorded on the compact disk 2, the sync pattern detection circuit45 detects the frame sync, and the M-series generation circuit 46generates the M-series random number data MZ corresponding to theM-series random number data MS for recording with reference to thedetected frame sync.

Furthermore, the edge detection circuit 44 detects the timing when thelaser beam crosses a pit edge, and the subcode detection circuit 42detects the timing when the subcode proceeds in seconds.

The analog digital conversion circuit 47 converts the reproductionsignal RF to a digital reproduction signal and the selector 49 selectsthe digital reproduction signal or the digital signal whose polarity isinverted with reference to the M-series random number data MZ, therebythe reproduction data RX which expresses the logical level of the diskdiscrimination code ED in the from of multi-value data is reproduced.

When in reproduction of the compact disk 2, the accumulator 53 and adder52 selectively accumulate the reproduction data RX corresponding to eachpit edge in seconds while the subcode proceeds step by step. The SNratio obtained by the reproduction result of the disk discriminationcode ED is thereby improved. The binarization circuit 54 binarizes theaccumulation result, thereby decoding the disk discrimination code ED,and then the disk discrimination code ED is subjected to errorcorrection process carried out by the ECC circuit 55 and supplied to thesystem control circuit 40.

When in reproduction of the disk discrimination code ED, although thereflectance change of an edge is small, the disk discrimination code EDis obtained as a total of signals obtained from many pit edges. The diskdiscrimination code ED can be decoded sufficiently and consistentlywithout any adverse effect of random noise on the disk. The adverseeffect caused by the level fluctuation of the whole reproduction signalis avoided effectively. When the disk discrimination code ED is decodedaccording to the total, because the disk discrimination code ED isdisturbed by the use of M-series during recording, it is possible toreproduce the disk discrimination code ED very stably.

(2-3) Effect of Another Embodiment

According to the configuration as described above, the laser beam isirradiated onto the compact disk, thereby changing the reflectance ofthe compact disk locally for forming a jitter and the diskdiscrimination code is recorded by the use of the jitter. The diskdiscrimination code is thus recorded so as to be reproduced by theoptical pickup which reproduces the digital audio signal and not to beillegally copied without any adverse effect on the reproduction of thedigital audio signal recorded in the form of pit strings.

Because 1 bit of the disk discrimination code is assigned to 1 secondwith reference to the subcode and 1 bit of the disk discrimination codeis assigned to at least 10 pit edges for recording, the diskdiscrimination code is reproduced consistently without any effect ofnoise on the reproduction.

Because the disk discrimination code is modulated with M-series randomdata for recording, the disk discrimination code is recorded so as notto be discriminated easily between noise and the disk discriminationcode itself. It is thus difficult to find and analyze the diskdiscrimination code. In addition, the disk discrimination code isreproduced consistently without any effect of noise on the reproduction.

Because the signal level of the reproduction signal RF is detected todecode the disk discrimination code and the signal level is accumulatedto remove the effect of noise mixed in the disk discrimination code inthe compact disk player, the disk discrimination code ED which isrecorded so as not to be discriminated from noise easily is reproducedconsistently.

Because the selector 49 selectively processes the digital reproductionsignal by the use of M-series random data MZ to reproduce the diskdiscrimination code, the disk discrimination code which is recorded soas not to be found nor analyzed is reproduced consistently.

(3) Further Another Embodiment

Although the case that the CD-R film structure is applied to thereflection recording film is described in the above-mentionedembodiment, the present invention is not limited only to the case; forexample, the film structure of a phase change type optical disk may beapplied, or this type of data may be additionally recorded on aconventional compact disk if it is possible to intermittently irradiatea laser beam with sufficiently high intensity.

Although the case that a mark is formed so as to cover astride a pitedge is described in the above-mentioned embodiment, the presentinvention is not limited only to the case; for example, this type ofmark may be formed near the edge to obtain the same effect as obtainedin the above-mentioned embodiment.

Although the M-series is reset in seconds in the above-mentionedembodiment, the present invention is not limited only to the case; forexample, the M-series may be reset with each CD frame to obtain the sameeffect as obtained in the above-mentioned embodiment.

Although the disk discrimination code is recorded in the above-mentionedembodiment, the present invention is not limited only to the case; forexample, various data required for decryption may be recorded if thedigital audio signal which is encrypted according to the pit and landlength is recorded, if the key information required for the encryptionis recorded, or if the data required for a key information selection ordecoding is recorded.

Although the disk discrimination code is recorded on a compact disk inthe above-mentioned embodiment, the present invention is not limitedonly to the case; for example, the reproduction or copy count may berecorded in application to a compact disk player.

Although the value accumulated by the accumulator is subjected to binarydiscrimination to reproduce the disk discrimination code in theabove-mentioned embodiment, the present invention is not limited only tothe case; for example, the accumulated value may be subjected tomulti-value discrimination for reproduction.

Although the EFM modulated digital audio signal is recorded in theabove-mentioned embodiment, the present invention is not limited only tothe case; for example, the present invention may be applied to variousmodulations such as 1-7 modulation, 8-16 modulation, and 2-7 modulation.

Although data is recorded in the form of pits and lands in theabove-mentioned embodiment, the present invention is not limited only tothe case; for example, the present invention may be applied widely torecord the desired data in the form of marks and spaces.

Although the present invention is applied to a compact disk and itsperipheral devices to record the audio signal in the above-mentionedembodiment, the present invention is not limited only to the case; forexample, the present invention may apply widely to various optical diskssuch as a video disk and its various peripheral devices.

(4-1) Configuration in Further Another Embodiment

FIG. 12 is a block diagram of the optical disk apparatus in furtheranother embodiment of the present invention.

This optical disk apparatus 1 records audio data D1 by exposing a laserbeam on a master disk 2. The audio data D1 is obtained from a digitalaudio recorder 3.

In detail, in the optical disk apparatus 1, a spindle motor 4 rotatesthe master disk 2 and an FG signal generation circuit held at the bottomof the spindle motor 4 outputs the FG signal FG whose signal level risesat each predetermined angle of rotation. A spindle servo circuit 5controls the rotation speed of the spindle motor 4 according to thelaser beam exposing position on the original disk 2 with reference tothis FG signal, thereby rotating the disk 2 at a predetermined rotationspeed.

A laser element 7 for recording comprises a gas laser element, etc. andirradiates a laser beam L1 to be exposed on the disk 2. An opticalmodulator 8A comprises, for example, an electric acoustooptic element.The optical modulator 8A subjects this laser beam L1 to on-offmodulation according to the EFM (Eight to Fourteen Modulation) signal S2output from the modulator 9 and outputs the modulated laser beam L2.

An optical deflector 8B comprises, for example, an electric acoustoopticelement. The optical deflector 8B diffracts the laser beam L2 outputfrom the optical deflector 8A according to the key modulation signal KSoutput from the key modulator 10, thereby changing the irradiationdirection of the laser beam L2 towards the inner/outer region of thedisk 2.

The mirror 12 folds the path of the laser beam L3 output from theoptical deflector 10, thereby outputting the laser beam L3 towards thedisk 2. The objective lens 13 converges the laser beam reflected fromthis mirror 12 on the recording face of the disk 2. Both the mirror 12and the objective lens 13 are moved by a thread mechanism (notillustrated) step by step towards the outer region of the disk 2 fromthe inner region synchronously with the rotation of the disk.

Consequently, the optical disk apparatus 1 can deviates the focal pointof the laser beam L3 step by step from the inner region to the outerregion of the disk 2, thereby forming a spiral track on the disk 2. Inaddition, the optical disk apparatus 1 controls the on/off status of thelaser beam L1 through the optical deflector 8A according to the EFMsignal S2 in this track forming processing, thereby forming pit stringssequentially along the track. Furthermore, the optical disk apparatus 1deviates the irradiation point of the laser beam L2 through the opticaldeflector 8B, thereby deviating each pit to the inner/outer region ofthe disk according to the key modulation signal KS.

In the optical disk apparatus 1, therefore, each pit is formed so as tominimize the deviation towards the inner/outer region of the disk 2 sothat data is reproduced from an optical disk manufactured on the basisof this master disk by controlling the tracking under the samecharacteristics as those of the conventional compact disk player, thatis, reproduction of recorded data is not disturbed by any pit string.More concretely, in this embodiment, the deviation of each pit to theinner/outer region of the disk is suppressed to not more than 1/50 ofthe track pitch even in the maximum deviation.

A digital audio tape recorder 3 outputs the audio data D1 to anencryption circuit 15. The encryption circuit 15 encrypts this audiodata according to the DES (Data Encryption Standard) code with referenceto the key information KY, then outputs the result.

A subcode generator 16 generates subcode data SC sequentially andoutputs the generated data SC in a predetermined format for the compactdisk. A modulation circuit 9 processes the output data S1 output fromthe encryption circuit 15, as well as the subcode SC, thereby generatingan EFM signal S2 in the predetermined compact disk format. In detail,the modulation circuit 9 adds a correction code to both output data S1output from the encryption circuit 15, as well as the subcode data SC,then interleaves and modulates the data so as to generate an EFM signalS2.

Consequently, in the optical disk apparatus 1, the audio data D1 can beencrypted and recorded in the form of pit strings on the original disk2.

A key modulation circuit 10 generates a key modulation signal KS fromthe key information KY and outputs the result. Consequently, in theoptical disk apparatus 1, the key information KY is recorded accordingto each bit which is deviated towards the inner/outer region of thedisk. In this optical disk apparatus 1, the key information KY isgenerated by the read-only memory, etc.

FIG. 13 is a detailed block diagram of this key modulation circuit 10.In the key modulation circuit 10, as shown in FIG. 14, the EFM signal S2(FIG. 14A) is input to the PLL circuit (Phase Locked Loop) 20 and itreproduces the clock CK (FIG. 14B) from the EFM signal S2 there.

A sync detection circuit 21 latches the EFM signal S2 sequentially withreference to the clock CK and determines the continued logic level ofthe signal S2, thereby detecting a sync pattern from the EFM signal S2.The sync detection circuit 21 outputs the frame clock FCK whose logiclevel rises at each sync pattern. Consequently, in the format of thecompact disk, a sync pattern is placed at the start of each frame andeach frame comprises 588 channel clocks. Consequently, the syncdetection circuit 21 comes to output the frame clock FCK whose logiclevel rises in units of 588 clocks.

A subcode detection circuit 22 monitors the EFM signal S2 with referenceto the clock CK and demodulates a subcode according to the EFM signalS2. In addition, the subcode detection circuit 22 monitors the timeinformation included in this demodulated subcode and outputs a 1-seconddetection pulse SECP whose signal level rises each time this timeinformation is changed for one second. Consequently, 98 frames areassigned to one second in the format of the compact disk, thereby thesubcode detection circuit 22 comes to output a 1-second detection pulseSECP so that its signal level rises in units of 98 pulses of the frameclock (FCK).

A counter 23 is a stepping counter for the frame clock FCK. If the1-second detection pulse SECP rises, the counter value CT is reset. Thecounter 23 is composed as a ring counter which circulates the countervalue CT in seconds. This counter value CT is changed synchronously withthe frame clock FCK.

A data selector 24 outputs its held data according to the counter valueCT of this counter 23, which is used as an address. The counter value CTof this counter 23 is changed cyclically in units of 98 frames persecond synchronously with the sync pattern. The data selector 24 thusoutputs 98 types of data one by one synchronously with the sync patternused as the address obtained from the counter value CT. The countervalue CT of the counter 23 is changed cyclically in seconds according tothe 1-second detection pulse SECP, thereby the data selector 24 repeatsthe output of these 98 types of data cyclically in seconds.

In this embodiment, the data selector 24 outputs 98-bit datasynchronously with the sync pattern by repeating the output of 1-bitdata assigned to each of 98 types of data in seconds. In addition, eachbit of the 54-bit key information KY is assigned to each predeterminedbit of the 98-bit data and a meaningless bit is assigned to each of theremaining 44 bits. In this embodiment, data KZ whose value is fixed isassigned to such meaningless data.

The M-series generation circuit 25 comprises a plurality of flip-flopcircuits and exclusive OR circuits connected serially respectively. TheM-series generation circuit 25 sets an initial value in each of thoseflip-flop circuits according to the frame clock FCK. In addition, theM-series generation circuit 25 transfers such the set data one by onesynchronously with the clock CK and generates M-series random numberdata MS in which logic levels 1 and 0 appear at the same probabilitybecause the values are fed back between predetermined stages.Consequently, the M-series generation circuit 25 outputs random numberdata MS, which is a binary series of a pseudo random number synchronizedwith the clock CK, so that the same pattern is repeated in one frameperiod, which is 588 clock cycles.

The exclusive OR circuit (X) 27 receives the random number data MS, aswell as the output data KD from the data selector 24, then outputs asignal MS1 of the exclusive OR of the data MS and KD (FIG. 14C). Indetail, the exclusive OR circuit 27 outputs the random number data MS asis if the logic value of the data KD output from the data selector 24 is0 and outputs the random number data MS with an inverted logic level ifthe logic level is 1. Consequently, the exclusive OR circuit 27 canmodulate the key information KY composing the output data KD with arandom number and output the modulated key information.

The flip-flop circuit 28 latches the output data MS1 from the exclusiveOR circuit 27 with reference to the rising edge of the EFM signal S2 andoutputs the latched data MS1 (FIG. 14D). In this embodiment, because thedisk 2 is exposed to a laser beam according to this EFM signal S2, thescanning start edge in each pit corresponds to the rising edge of theEFM signal S2 on an optical disk manufactured on the basis of thismaster disk 2. Consequently, the flip-flop circuit 28 holds the logiclevel of the latched data MS1 within a period between when the data MS1is output sequentially from the exclusive OR circuit 27 at the clockcycle which is a reference period for forming each pit and when theoutput data MS1 assigned to a timing for starting each pit is latchedand the forming of at least one pit is finished.

An amplifier circuit 29 is a driver amplifier for driving the opticaldeflector 8B and amplifies the output signal from the flip-flop 28 andoutputs the amplified signal to the optical deflector 8B as a keymodulation signal KS. Consequently, the amplification circuit 29 candeviate the irradiation point of the laser beam in bits towards theinner/outer region of the original disk 2. In the amplifier circuit 29,the gain is set so that this positional deviation is limited to not morethan 1/50 of the track pitch in maximum. The optical disk apparatus 1can thus be prevented from reproducing failures of data recorded in theform of pit strings.

In this embodiment, therefore, the original disk 2 exposed to the laserbeam such way is developed and treated for electroforming, therebymanufacturing a mother disk. This mother disk is then used tomanufacture a stamper. In addition, this stamper is used to manufactureoptical disks in the same way as the ordinary compact disk manufacturingprocess.

Consequently, in this embodiment, an optical disk can be manufactured sothat audio data D1 encrypted in the form of pit strings is recorded andthe key information KY is recorded with a deviation of each pit Ptowards the inner/outer region of the optical disk (FIG. 14E-2). Inother words, in an ordinary compact disk, pits P are formed on the trackcenter one by one along the track according to the EFM signal S2 andaudio data is recorded according to the length of each pit and theinterval between pits (FIG. 14E-1). On the contrary, in the case of theoptical disk in this embodiment, audio data to be recorded is alreadyencrypted according to the length of each pit and the interval betweenpits, and the key information KY for decrypting the encryption of thisaudio data is recorded according to the deviation of each pit towardsthe inner/outer region of the optical disk.

FIG. 15 is a block diagram of an optical disk apparatus 30 forreproducing data from an optical disk 31 manufactured as describedabove. In this optical disk apparatus 30, a spindle motor 32 rotates theoptical disk 31 at a consistent linear speed under the control of aservo circuit 33.

An optical pickup 34 irradiates a laser beam on the optical disk 31 andreceives the reflected laser beam at a predetermined beam receptionelement, then outputs a reproduction signal RF whose signal level ischanged according to the intensity of the reflected laser beam at thisreception element. The reproduction signal RF changes its levelaccording to each pit recorded on the optical disk 31.

Furthermore, the optical pickup 34 processes the reflected laser beamwhich is received at the beam reception element with the use of aso-called push-pull method, thereby generating a push-pull signal PPwhose signal level is changed according to the position of each pit withrespect to the laser beam irradiation point at the inner/outer region ofthe optical disk 31. The optical pickup 34 outputs a focus error signalwhose signal level is changed according to the amount of the focuserror.

In the servo circuit 33, this push-pull signal PP is used to limitfrequency bands, thereby generating a tracking error signal whose signallevel is changed according to the deviation of the laser beamirradiation point from the track center. And, this tracking error signalis used to control the tracking of the optical pickup 34. The servocircuit 33 controls the focusing of the optical pickup 34 with the useof the focus error signal.

A high-pass filter (HPF) 35 cuts the low frequency components of thepush-pull signal PP, thereby removing the deviation of the laser beamirradiation point from the track center from the push-pull signal PPwhose signal level is changed according to the position of each pit fromthis track center. Consequently, the high-pass filter (HPF) 35 detectsthe deviation detection signal HPP whose signal level is changedaccording to the deviation of each pit from the track center.

A binary circuit 36 binarizes the reproduction signal RF at apredetermined reference level, thereby generating a binary signal BD.

A PLL circuit 37 operates with reference to this binary signal BD,thereby reproducing a channel clock CCK of the reproduction signal RF.

An EFM demodulation circuit 38 latches the binary signal BD sequentiallywith reference to the channel clock CCK, thereby reproducing the datacorresponding to the EFM demodulation signal S2. In addition, the EFMdemodulation circuit 38, after demodulating this reproduced data to EFMone, delimits this demodulated data in units of 8 bits with reference tothe frame sync and deinterleaves each generated 8-bit signal and outputsthe result to an ECC (Error Correcting Code) circuit 39.

The ECC circuit 39 corrects errors in this output data according to theerror correcting code added to the output data from this EFMdemodulation circuit 38, then reproduces encrypted audio data andoutputs the reproduced data.

A cryptogram processing circuit 40 decrypts audio data according to thekey information KY detected by the key detection circuit 42 and outputsthe decrypted data.

A digital/analog conversion circuit (D/A) 41 converts digital audio dataD1 output from this cryptogram processing circuit 40 to analog data andoutputs analog audio data S4.

A key detection circuit 42 processes the deviation detection signal HPPwith reference to the channel clock CCK and the binary signal BD,thereby reproducing the key information KY and outputting the reproduceddata to the cryptogram processing circuit 40.

FIG. 16 is a detailed block diagram of a key detection circuit 42. Inthe key detection circuit 42, a subcode detection circuit 52 monitorsthe binary signal BD with reference to the channel clock CCK anddemodulates the subcode information from this binary signal BD. Inaddition, the subcode detection circuit 52 monitors the time informationincluded in the demodulated subcode information and outputs a 1-seconddetection pulse SECP whose signal level rises each time this timeinformation is kept changed for one second.

A pit detection circuit 54 latches the binary signal BD sequentially atthe timing of the channel clock CCK and compares continuous two latchedBD signals with each other, thereby detecting the pit rising timingaccording to the result of the comparison. The pit detection circuit 54outputs an edge detection signal PT at the pit rising timing accordingto this result of comparison. The pit detection circuit 54 furtherdetects the pit falling timing in the same way and outputs a centerdetection signal CTP around the center of each pit according to thedetection result of the corresponding pit rising timing.

A sync detection circuit 55 latches the binary signal BD sequentiallywith reference to the channel clock CCK and determines the continuedlogic level of the binary signal BD, thereby detecting a sync pattern.Consequently, as shown in FIG. 17, the sync detection circuit 55generates a set pulse FSET (FIGS. 17A3, 17B, and 17D) whose signal levelrises only for one clock period at the sync pattern starting timing anda clear pulse FCLR (FIG. 17C) whose signal level rises with a delay ofone clock cycle from this set pulse FSET and outputs those pulses.

Consequently, because a sync pattern is detected in units of 588 clockcycles and 98 times per second in the binary reproduction signal BD(FIGS. 17A1 and 17A2), the sync detection circuit 55 can output theclear pulse FCLR and the set pulse FSET synchronously with this syncpattern.

An M-series generation circuit 56 initializes each address withreference to the clear pulse FCLR, then accesses the built-in read-onlymemory address by address according to the channel clock CCK, therebygenerating M-series random number data MX corresponding to the M-seriesrandom number data MS generated in the optical disk apparatus 1.

Consequently, the key detection circuit 42 can reproduce variousreference signals necessary for reproducing the key information KY withrespect to the processing carried out in the optical disk apparatus 1.

In the key detection circuit 42, an analog/digital (A/D) conversioncircuit 57 converts the analog deviation detection signal HPP to adigital HPP signal with reference to the channel clock CCK, then outputsan 8-bit digital reproduction signal. A polarity inversion circuit (−1)58 inverts the polarity of this digital reproduction signal and outputsthe polarity-inverted signal.

A latching circuit 59 latches M-series random number data MX at a timingof the edge detection signal PT and holds this latched data MX within atime between when the exclusive OR circuit processes the data MX in thekey modulation circuit 10 as described with reference to FIG. 13, thatis, when forming of a pit is started, and when forming of the pit iscompleted.

A selector 60 selects the digital signal entered directly from the A/Dconversion circuit 57 or the polarity-inverted digital signal enteredfrom the polarity inversion circuit 58 according to the logic level ofthe output data MZ output from the latching circuit 59 and outputs theselected signal. In other words, the selector selects and outputs thedigital signal entered directly when the logic level of the data MZ is 1and the polarity-inverted digital signal when the logic level of thedata MZ is 0. Consequently, this selector 60 comes to reproduce thelogic level of the key information KY (KD) modulated with the M-seriesrandom number data MS with the use of multi-value data and outputs thedata RX reproduced with the use of this multi-value data.

An adder 62 is a 16-bit digital adder and adds up the reproduced data RXand the output data AX output from the accumulator (ACU) 63 and outputsthe total. The accumulator 63 comprises a 16-bit memory for holding theoutput data from the adder 62. The accumulator 63 feeds back its helddata to the adder 62, thereby composing a cumulative adder together withthe adder 62. In other words, the accumulator 63 clears itself with theclear pulse FCLR, then accumulates the output data from the adder 62synchronously with the output signal CTP from the pit detection circuit54.

Consequently, the adder 62 and the accumulator 63 are combined to add upor subtract the deviation value detected in the center of each pitaccording to the M-series random number data MS. This adding/subtractingprocessing is repeated for each frame period.

A binary circuit 64 binarizes the output data AX from the accumulator 63according to a predetermined reference value and outputs the binarizeddata. Consequently, the binarization circuit 64 can convert the data RXreproduced from the key information KY (KD) with the use of amulti-value data reproduced by the selector 60 to binary data.

A shift register (SR) 65 is a 98-bit shift register. The shift register(SR) 65 receives binary data output from the binary circuit 64sequentially at the set pulse FSET rising timing, then transfers thedata.

A flip-flop circuit (F/F) 66 fetches data output from the shift register65 in a bit-parallel manner at a timing of the 1-second detection pulseSECP and holds the data. Consequently, the flip-flop circuit 66 in thekey detection circuit 42 can hold the data KD consisting of keyinformation KY and fixed value data KZ. The key detection circuit 42outputs a predetermined bit held in this flip-flop circuit 66selectively, thereby supplying key information KY to the cryptogramprocessing circuit 40 and decrypting encrypted audio data.

(4-2) Operation in Further Another Embodiment

In the above configuration, the optical disk apparatus 1 (FIG. 12)exposes a laser beam on the original disk 2 in the manufacturing processof the optical disk 31 in this embodiment and this original disk 2 isdeveloped and treated for electroforming, thereby manufacturing a motherdisk. Then, this mother disk is used to manufacture a stamper and anoptical disk.

When exposing a laser beam on this master disk 2, in the optical diskapparatus 1, the audio data D1 output from the digital audio taperecorder 3 is entered to the encryption circuit 15 and encrypted therewith the use of predetermined key information KY. Consequently, theaudio data D1 is processed so as not to be reproduced without this keyinformation KY. After this, the audio data D1 is converted to an EFMsignal S2 in the modulation circuit 9 in the same way as theconventional compact disk.

In the optical disk apparatus 1, this EFM signal S2 controls the on/offstatus of the laser beam L1 and this controlled laser beam L2 isconverged sequentially from the inner region to the outer region of themaster disk 2, thereby forming a spiral track on the object optical diskfrom the inner region to the outer region. The encrypted audio data D1is thus recorded in the form of pit strings along this track.

While the audio data D1 is recorded in the form of pit strings such way,the key modulation circuit 10 in the optical disk apparatus 1 canmodulate the key information KY so as not to be decrypted easily,thereby generating a key modulation signal KS. And, this key modulationsignal KS drives the optical deflector 8B and deviates the focal pointof the laser beam L3 towards the inner/outer region of the original disk2. The key information KY is thus recorded according to the deviation ofeach pit towards the inner/outer region of the disk 2.

In this embodiment, therefore, it is possible to provide the audio dataD1 encrypted so as not to be reproduced without the key information KY,as well as the key information KY recorded together on one medium.

The positional deviation of each pit formed as described above islimited to not more than 1/50 of the track pitch, thereby the pit isdeviated cannot be recognized easily even by the use of a microscope.This makes it very difficult to analyze such the positional deviation ofeach pit, so that the optical disk can be protected effectively fromillegal copying.

In addition, because the positional deviation is very small,reproduction signals can be reproduced surely with the margins enough inboth phase and amplitude. The audio data D1 recorded in the form of pitstrings can thus be reproduced certainly. Such the deviation of a pittowards the inner/outer region of the disk affects the controlling ofthe tracking some times, but such a small deviation of the pit in thisembodiment never disturbs the accuracy of the tracking. Audio datarecorded in the form of pits can thus be reproduced accurately enoughfor practical use.

In detail, the key information KY (FIG. 13), because 98 frames areassigned to one second on a compact disk, is set in the data selector 24so that data KZ consisting of 44 meaningless fixed bits are added to thekey information KY consisting of a 54-bit DES code when one bit data isassigned to each frame.

The key information KY(KD) set so that one bit is assigned to one frameis output from the data selector 24 so as to be circulated in secondsaccording to the sync pattern detected in the sync detection circuit 21and the SECP detected in seconds in the subcode detection circuit 22.

At the same time, the M-series generation circuit 25 generates randomnumber data MS, which is a binary series in which logic levels 1 and 0appear at the same probability synchronously with the clock CK andrepetitively in frames according to the FCK indicating a detected syncpattern.

The key information KY(KD) is output from the data selector 24 andmodulated with random number data MS when the exclusive OR circuit 27obtains an exclusive OR from between the key information KY(KD) and therandom number data MS. At this time, because this random number data MSis a binary series in which logic levels 1 and 0 appear at the sameprobability, the modulated output data from the exclusive OR circuit 27enables logic levels 1 and 0 to appear at almost the same probability.

In the key modulation circuit 10, the output data MS1 generated such wayis latched by the flip-flop 28 at the rising of the EFM signal S2,thereby one bit of the output data MS1 is assigned selectively in eachpit formed on the original disk 2. And, according to the logic level ofthis one bit, the focal point of the laser beam L3 is deflected towardsthe inner/outer region of the disk 2 by the optical deflector 8B, sothat the key information KY is recorded according to this deflectiontowards the inner/outer region of the disk 2.

In this embodiment, the key information KY(KD) is output from the dataselector in units of a single bit per frame and this key informationKY(KD) is modulated with random number data MS, thereby the pit P isdeviated in position. On the optical disk, therefore, the pit P isdeviated irregularly towards the inner/outer region of the optical disk2.

In this embodiment, therefore, the bits of the key information KY(KD)are recorded in a plurality of pits in a distributed manner, so that itis very difficult to find the key information KY recorded in such pitsdeviated at random from the center of the track. More concretely, evenwhen the data recording face of the optical disk is checked with amicroscope, a bit string is just seen as if modulated with a noise, thusit is very difficult to find such the key information KY visually.Consequently, because one bit of the key information KY is assigned tothe 588 channel clocks in this case, at least one bit of the keyinformation KY comes to be recorded in not less than 50 pits in adistributed manner.

Furthermore, because logic levels 1 and 0 appear at the same probabilityin the random number data MS at this time, pits are also formed so as tobe deviated towards the inner and outer regions from the track center atalmost the same probability. And, because such the positional deviationof each pit is very small, the deviation of the pit is just recognizedas a noise mixture when observing various signals obtained from theoptical pickup with the use of a microscope. It is thus very difficultto check from the waveforms of those signals whether or not the keyinformation KY exists.

On the other hand, suck the deviation of each pit does not include anyoffset component which is a DC component. In addition, because theoutput data MS1 is latched by the flip-flop circuit 28 and each pit isdeviated in position according to the data MS1, this deviation of thepit can be detected easily, although an extremely degraded SN is usedfor the detection. The SN is obtained by extracting the high bandcomponents from the push-pull signal PP for detecting the tracking errorsignal. Consequently, this optical disk can be protected from illegalcopying while it is structured simply so as to reproduce the keyinformation KY with the use of a conventional optical pickup.

More concretely, just like in the conventional compact disk player, theoptical disk apparatus 30 manufactured as described above allows thereproduction signal RF to be binarized in the binarization circuit 36,then processed in the EFM demodulation circuit 38. Furthermore, theerrors in the signal RF can be corrected in the following ECC circuit39, thereby encrypted audio data is reproduced. In the followingcryptogram processing circuit 40, audio data is decrypted according tothe key information KY obtained separately, so that audio signalsrecorded in the form of pit strings can be reproduced as a sound throughthe D/A conversion circuit 41.

In the optical disk apparatus 30, the band of the push-pull signal PPobtained through the optical pickup 34 is limited by the high passfilter 35, thereby it is possible to detect the off-track-centerdetection signal HPP whose signal level is changed according to thedeviation of each pit towards the inner/outer region of the optical disk2 with a simple structure.

Furthermore, in the optical disk apparatus 30, this deviation detectionsignal HPP is processed by the key detection circuit 42, so that the keyinformation KY can be reproduced.

In detail, in the key detection circuit 42, the deviation detectionsignal HPP is converted to a digital signal by the A/D conversioncircuit 57 in channel clocks, then the polarity is inverted by thepolarity inversion circuit 58.

These two types of digital signals are entered to the adder 62selectively according to the output data MZ. The data MZ is generated asa result of the latching of the random number data MX by the latchingcircuit 59 corresponding to a pit with reference to the sync pattern ofthe binary signal BD. The digital signal selected and entered to theadder 62 such way is accumulated there with reference to the FCLR, whichis a detected sync pattern.

In detail, when in recording, the output data from the A/D conversioncircuit 57 is added or subtracted according to the logic level of theoutput data from the exclusive OR circuit 27 (FIG. 13) at the risingtiming of the EFM signal S2, and the accumulated value AX which is aresult of addition or subtraction is accumulated in the accumulator 63for each frame. In addition, the accumulated value AX in thisaccumulator 63, which is a binary discrimination result, is fetched intothe shift register 65 when a sync pattern is started, thereby the keyinformation KY is demodulated.

Consequently, because the deviation of each pit is so small and thedeviation detection signal HPP obtained from each pit is accumulated forone frame such way so as to be subjected to binary discrimination evenwith an extremely degraded S/N ratio, the key information KY can bereproduced after the binary discrimination with a high S/N ratio. Thekey information KY can thus be reproduced certainly, while it isrecorded so as not to be found easily.

In the key detection circuit 42, the accumulator 63 fetches data fromthe adder 62 corresponding to the center of each pit when the circuit 42accumulates the signal level of the deviation detection signal HPP.Consequently, the signal level of the deviation detection signal HPP isaccumulated at a stable timing, thereby the key detection circuit 42 ismuch more improved for the detection accuracy.

Illegal copying from the master optical disk 2 described above mightalso be done by controlling the on/off status of the laser beam with theuse of the binary signal BD output from the binary circuit 36. In suchthe illegal copying, however, it is very difficult to record the keyinformation KY depending on the disposition of each pit deviated fromthe track center. This makes it very difficult to copy the master disk31 illegally in this embodiment.

In the case that audio data is reproduced from an optical disk copiedillegally by copying only the pit strings such way, the key informationKY recorded according to the pits deviated from the track center willnot be copied, so that audio signals are output just like an encryptednoise. The recorded music, therefore, will not be reproduced normally,thereby the illegally copied optical disk becomes useless, thus illegalcopying is prevented.

In this embodiment, therefore, key information can be recorded so as bereproduced with an optical pickup for reproducing audio data and not tobe copied illegally without any adverse effect on reproduction of audiodata recorded in the form of pit strings.

(4-3) Effect of Further Another Effective Embodiment

According to the configuration of the optical disk apparatus asdescribed above, because key information is recorded in the form of pitsso as to be deviated from the track center towards the inner/outerregion of the disk, key information can be recorded so as be reproducedwith an optical pickup for reproducing audio data and not to be copiedillegally without any adverse effect on the reproduction of the audiodata recorded in the form of pit strings. Consequently, the audio dataencrypted with this key information can be recorded in the form of pitstrings so as to be protected from illegal copying effectively.

In addition, because key information is modulated with a binary seriesbefore it is recorded, it is difficult to find such the key informationrecorded in the form of pits deviated from the track center and it iseffectively prevented from illegal copying.

In addition, because an M-series random numbers causing logic levels 1and 0 to appear at the same probability is employed for the binaryseries, output signals from the optical pickup are observed like a noisemixture, thereby the recorded key information cannot be found easily andprotected effectively from illegal copying.

This embodiment also makes it possible to assign one bit of the keyinformation to at least 50 pits and to dispose these pits so as to bedeviated from the track center very slightly, thereby the recorded keyinformation can be reproduced certainly.

In detail, the logic level of a binary series is referenced to integratethe signal level of the deviation detection signal. It is thus possibleto reproduce the key information recorded so as to be deviated veryslightly from the track center.

In addition, because the deviation of each pit from the track center islimited to not more than 1/50 of the track pitch, it is difficult tofind the key information recorded in the form of pits deviated such wayslightly.

(5) Further Another Embodiment

Although one bit of key information is assigned to one frame in theabove embodiment, the present invention is not limited only to the case;for example, a plurality of bits of the key information may be assignedto one frame and furthermore, one bit of the key information may beassigned to a plurality of frames. And, instead of the assignment ofsuch key information bits with reference to a frame of audio data, onebit of key information may be assigned with reference to the number ofpits.

Although one bit of key information is recorded in not less than 50 pitsin a distributed manner by assigning one bit of the key information toone frame in the above embodiment, the present invention is not limitedonly to the case; for example, the number of pits to be assigned to onebit may be varied as needed. As a result of testing, it is found thatkey information can be reproduced at an S/N ratio satisfactorily enoughfor practical use if one bit of key information is assigned to not lessthan 20 pits.

Although key information is recorded with the use of added meaninglessfixed bits in the above embodiment, the present invention is not limitedonly to the case; for example, an error correcting code and/or copyrightdata, etc. may be added to the key information to be recorded.

Although encrypted data is recorded in the form of pit strings and keyinformation required for decrypting data is also recorded in the form ofpits deviated from the track center towards the inner/outer region ofthe disk in the above embodiment, the present invention is not limitedonly to the case; for example, the key information may be replaced withanother kind of data such as discrimination data for whether to enableor disable copying.

Although the accumulated value in the accumulator is subjected to binarydiscrimination, thereby reproducing the key information in the aboveembodiment, the present invention is not limited only to the case; forexample, this accumulated value may be subjected to multi-valuediscrimination. In this case, multi-value data can be recorded in pitsdeviated from the track center.

Although digital audio signals are modulated to EFM signals before theyare recorded in the above embodiment, the present invention is notlimited only to the case; for example, the digital audio signals may bemodulated in various modulations such as 1-7, 8-1, 2-7 modulations.

Although key information is recorded on the entire surface of theoptical disk in the above embodiment, the present invention is notlimited only to the case; for example, the key information may berecorded only in such a limited region as a lead-in area.

Although desired data is recorded in the form of pit strings in theabove embodiment, the present invention is not limited only to the case;for example, desired data may be recorded in the form of mark strings.

Although the present invention applies to an optical disk for recordingaudio data and its peripheral devices, thereby recording audio signals,the present invention is not limited only to the case; for example, thepresent invention may apply to various types of optical disks such as avideo disk, as well as its peripheral devices.

As described above, according to the optical disk apparatus in thisembodiment, the worth of each pirated version optical disk can bedegraded significantly even when any of the above methods is used,thereby the popularization of such pirated version optical disks can beprevented.

Furthermore, according to the present invention, because the reflectanceof the optical disk is locally changed to give a jitter to each edgeposition information and desired data is additionally recorded by theuse of the jitter, such data as disc discrimination code is recordedwithout any adverse effect on the reproduction of the data stringrecorded in the form of pit strings so as to be reproduced by theoptical pickup which is served for reproducing the data strings and soas not to be copied illegally.

Furthermore, according to the present invention, because such subdata askey information is recorded in the form of pits deviated from the trackcenter towards the inner/outer region of the optical disk, various datacan be recorded so as to be produced with an optical pickup forreproducing data strings recorded in the form of pit strings and not tobe copied illegally depending on the copying method.

1. An optical disc apparatus, comprising: main modulation signalgenerating means for generating a main modulation signal according tomain data; laser beam irradiating means for irradiating a laser beam onsaid optical disk according to said main modulation signal, therebyforming a pit string or a mark string on said optical disk; modulationsignal generating means for generating a sub-modulation signal accordingto subdata; and deviating means for deviating an irradiation point ofsaid laser beam towards the inner/outer region of said disc to expresssaid sub-modulation signal.
 2. An optical disk apparatus in accordancewith claim 1, wherein said sub-modulation signal generating meanscomprises: timing detecting means for detecting a timing of an edge ofsaid pit or mark and outputting said detected timing; binary numberseries generating means for generating a predetermined binary numberseries; and modulating means for generating said sub-modulation signalfrom said subdata according to said binary number series and saiddetected timing.
 3. An optical disk apparatus in accordance with claim2, wherein said binary number series is an M-series random number.
 4. Anoptical disk apparatus in accordance with claim 1, wherein said mainmodulation signal generating means generates said main modulation signalby encrypting said main data with said subdata.
 5. An optical diskapparatus in accordance with claim 1, wherein said main modulationsignal generating means generates said main modulation signal so thatthe intensity of said laser beam is changed in a period decided by anintegral multiple of a predetermined basic period.
 6. An optical diskapparatus in accordance with claim 1, wherein said sub-modulation signalgenerating means generates said sub-modulation signal so that not lessthan 20 pits or marks correspond to one bit of said subdata.
 7. A methodfor recording data on an optical disk comprising: generating a mainmodulation signal according to main data; forming a pit string or a markstring on said optical disk by irradiating a laser beam on said opticaldisk according to said main modulation signal; generating asub-modulation signal according to subdata; and deviating theirradiation point of said laser beam toward the inner/outer region ofsaid optical disk to said sub-modulation signal.
 8. A method forrecording data on an optical disk in accordance with claim 7, whereinsaid sub-modulation signal is generated from said subdata according to atiming corresponding to said pit or mark edge and a predetermined binarynumber series.
 9. A method for recording data on an optical disk inaccordance with claim 8, wherein said binary number series is anM-series random number.
 10. A method for recording data on an opticaldisk in accordance with claim 7, wherein said main modulation signal isgenerated by encrypting said main data according to said subdata.
 11. Amethod for recording data on an optical disk in accordance with claim 7,wherein said main modulation signal is generated so that an intensity ofsaid laser beam is changed in a period decided by an integral multipleof a predetermined basic period.
 12. A method for recording data on anoptical disk in accordance with claim 7, wherein said sub-modulationsignal is generated so that one bit of said subdata corresponds to notless than 20 of said pits or marks.
 13. An optical disk having a pitstring or a mark string formed along a spiral or concentrical track,comprising main data recorded on said optical disk according to thelength of said pit or mark and the interval between said pits or marksformed along said track; and sub-data recorded on said optical diskaccording to the deviation of said pit or mark towards the inner/outerregion of the disc from the center of said track.
 14. An optical disk inaccordance with claim 13, wherein said pit or mark is deviatedcorresponding to a calculation processing result of said sub-data and apredetermined binary number series.
 15. An optical disk in accordancewith claim 14, wherein said binary number series is an M-series randomnumber.
 16. An optical disk in accordance with claim 13, wherein saidmain data is encrypted with said sub-data before it is recorded on saidoptical disk.
 17. An optical disk in accordance with claim 13, whereinone bit of said sub-data is assigned to not less than 20 of said pits ormarks.
 18. An optical disk in accordance with claim 13, wherein thedeviation of said pit or mark is set to not more than 1/50 of a trackpitch towards the inner/outer region of said optical disk from a centerof said track.
 19. An optical disk reproducing apparatus, comprising:reproduction signal detecting means for detecting a reproduction signalfrom a reflected beam of a laser beam irradiated on an optical disk, asignal level of said reproduction signal being changed according to apit string or a mark string formed on said optical disk; maindemodulating means for reproducing main data recorded in a form of saidpit strings or mark strings by subjecting said reproduction signal tobinary-discrimination; deviation detecting means for outputting adeviation detection signal whose level is changed according to adeviation of said pit or mark towards the inner/outer region of saidoptical disk from a center of a track; and sub-modulating means forreproducing subdata recorded according to the deviation of said pit ormark towards the inner/outer region of said optical disk from the centerof said track by processing said deviation detection signal withreference to said reproduction signal.
 20. An optical disk reproducingapparatus in accordance with claim 19, wherein said sub-demodulatingmeans comprises: binary number series generating means for generating abinary number series whose bit is changed corresponding to said pit ormark; integrating means for integrating a signal level of said deviationdetecting signal with reference to a logical level of said binary numberseries; and integrating result processing means for detecting saidsubdata by processing said integration result.
 21. An optical diskreproducing apparatus in accordance with claim 20, wherein said binarynumber series is an M-series random number.
 22. An optical diskreproducing appartus in accordance with claim 19, wherein said maindemodulating means outputs said main data by decrypting an encryptionthereof with said subdata.
 23. An optical disk reproducing method,comprising: reproducing main data recorded in a form of pit strings ormark strings from a reflected beam of a laser beam irradiated on saidoptical disk; and reproducing subdata recorded according to a deviationof said pit or mark towards an inner/outer region of said optical diskfrom a center of a track.
 24. An optical disc apparatus, comprising: amain modulator configured to generate a main modulation signal accordingto main data; a laser configured to irradiate a laser beam on saidoptical disk according to said main modulation signal, thereby forming apit string or a mark string on said optical disk; a modulation signalunit configured to generate a sub-modulation signal according tosubdata; and a deviating unit configured to deviate an irradiation pointof said laser beam towards the inner/outer region of said disc toexpress said sub-modulation signal.
 25. An optical disk reproducingapparatus, comprising: a reproduction signal detecting unit configuredto detect a reproduction signal from a reflected beam of a laser beamirradiated on an optical disk, a signal level of said reproductionsignal being changed according to a pit string or a mark string formedon said optical disk; a main demodulating unit configured to reproducemain data recorded in a form of said pit strings or mark strings bysubjecting said reproduction signal to binary-discrimination; adeviation detecting unit configured to output deviation detection signalwhose level is changed according to a deviation of said pit or marktowards the inner/outer region of said optical disk from a center of atrack; and a sub-modulating unit configured to reproduce subdatarecorded according to the deviation of said pit or mark towards theinner/outer region of said optical disk from the center of said track byprocessing said deviation detection signal with reference to saidreproduction signal.